Color chrome and nickel difference. The marriage of the coating is shiny nickel-chrome. What is nickel and what is it for?

Nickel-plated coatings have a number of valuable properties: they are well polished, acquiring a beautiful long-lasting mirror finish, they are durable and well protect the metal from corrosion.

The color of nickel plating is silvery white with a yellowish tint; they are easily polished, but fade over time. The coatings are characterized by a fine-grained structure, good adhesion to steel and copper substrates, and the ability to passivate in air.

Nickel plating is widely used as a decorative coating for parts of lamps intended for lighting public and residential premises.

To cover steel products, nickel plating is often carried out over an intermediate copper sublayer. Sometimes a three-layer nickel-copper-nickel coating is used. In some cases, a thin layer of chromium is applied to the nickel layer, and a nickel-chromium coating is formed. On parts made of copper and alloys based on it, nickel is applied without an intermediate sublayer. The total thickness of two and three-layer coatings is regulated by mechanical engineering standards, usually it is 25–30 microns.

On parts intended for operation in a humid tropical climate, the coating thickness should be at least 45 microns. In this case, the regulated thickness of the nickel layer is not less than 12–25 µm.

To obtain brilliant coatings, nickel-plated parts are polished. Recently, brilliant nickel plating has been widely used, which eliminates the laborious operation of mechanical polishing. Brilliant nickel plating is achieved by introducing brighteners into the electrolyte. However, the decorative qualities of mechanically polished surfaces are higher than those obtained by bright nickel plating.

Nickel deposition occurs with significant cathodic polarization, which depends on the temperature of the electrolyte, its concentration, composition, and some other factors.

Electrolytes for nickel plating are relatively simple in composition. Currently, sulfate, hydroboric fluoride and sulfamic electrolytes are used. Lighting factories use exclusively sulfate electrolytes, which allow them to work with high current densities and at the same time obtain high-quality coatings. The composition of these electrolytes includes salts containing nickel, buffer compounds, stabilizers and salts that contribute to the dissolution of the anodes.

The advantages of these electrolytes are the lack of components, high stability and low aggressiveness. Electrolytes allow a high concentration of nickel salt in their composition, which makes it possible to increase the cathode current density and, consequently, to increase the productivity of the process.

Sulfate electrolytes have high electrical conductivity and good dissipation ability.

An electrolyte of the following composition, g/l, has been widely used:

NiSO4 7H2O240–250

*Or NiCl2 6H2O - 45 g/l.

Nickel plating is carried out at a temperature of 60°C, pH=5.6÷6.2 and a cathodic current density of 3–4 A/dm2.

Depending on the composition of the bath and its mode of operation, coatings with varying degrees of gloss can be obtained. For these purposes, several electrolytes have been developed, the compositions of which are given below, g/l:

for matte finish:

NiSO4 7H2O180–200

Na2SO4 10H2O80–100

Nickel plated at a temperature of 25–30°C, at a cathodic current density of 0.5–1.0 A/dm2 and pH=5.0÷5.5;

for a semi-gloss finish:

Nickel sulfate NiSO4 7H2O200–300

Boric acid H3BO330

2,6–2,7-Disulfonaphthalic acid5

Sodium fluoride NaF5

Sodium chloride NaCl7–10

Nickel plating is carried out at a temperature of 20–35°C, cathodic current density 1–2 A/dm2 and pH=5.5÷5.8;

for a shiny finish:

Nickel sulfate (hydrate) 260–300

Nickel chloride (hydrate) 40–60

Boric acid30–35

Saccharin0.8–1.5

1,4-butyndiol (in terms of 100%) 0.12-0.15

Phthalimide 0.08–0.1

Nickel plating operating temperature 50–60°C, electrolyte pH 3.5–5, cathodic current density with intensive stirring and continuous filtration 2–12 A/dm2, anode current density 1–2 A/dm2.

A feature of nickel plating is a narrow range of electrolyte acidity, current density and temperature.

To maintain the composition of the electrolyte within the required limits, buffer compounds are introduced into it, which are most often used as boric acid or a mixture of boric acid with sodium fluoride. In some electrolytes, citric, tartaric, acetic acid or their alkaline salts are used as buffer compounds.

A feature of nickel coatings is their porosity. In some cases, dotted spots, the so-called "pitting", may appear on the surface.

To prevent pitting, intensive air mixing of the baths and shaking of the suspensions with parts attached to them are used. The reduction of pitting is facilitated by the introduction of surface tension reducers or wetting agents into the electrolyte, which are used as sodium lauryl sulfate, sodium alkyl sulfate and other sulfates.

The domestic industry produces a good anti-pitting detergent "Progress", which is added to the bath in an amount of 0.5 mg / l.

Nickel plating is very sensitive to impurities that enter the solution from the surface of parts or due to anodic dissolution. When nickel plating steel de-

hoists, the solution is clogged with iron impurities, and when coating copper-based alloys - with its impurities. Impurities are removed by alkalizing the solution with carbonate or nickel hydroxide.

Organic pitting contaminants are removed by boiling the solution. Sometimes nickel-plated parts are tinted. In this case, colored surfaces with a metallic sheen are obtained.

Toning is carried out by a chemical or electrochemical method. Its essence lies in the formation of a thin film on the surface of the nickel coating, in which light interference occurs. Such films are obtained by applying organic coatings several micrometers thick to nickel-plated surfaces, for which the parts are treated in special solutions.

Black nickel coatings have good decorative qualities. These coatings are obtained in electrolytes in which zinc sulfates are added in addition to nickel sulfates.

The composition of the electrolyte for black nickel plating is as follows, g/l:

Nickel sulfate40–50

Zinc sulfate20–30

Potassium thiocyanate25–32

Ammonium sulphate12–15

Nickel plating is carried out at a temperature of 18–35°C, cathodic current density of 0.1 A/dm2 and pH=5.0÷5.5.

2. CHROME PLATE

Chrome coatings have high hardness and wear resistance, low coefficient of friction, are resistant to mercury, adhere strongly to the base metal, and are chemically and heat resistant.

In the manufacture of lamps, chromium plating is used to obtain protective and decorative coatings, as well as reflective coatings in the manufacture of mirror reflectors.

Chrome plating is carried out on a pre-applied copper-nickel or nickel-copper-nickel sublayer. The thickness of the chromium layer with such a coating usually does not exceed 1 μm. In the manufacture of reflectors, chromium plating is currently being replaced by other coating methods, but in some factories it is still used for the manufacture of reflectors for mirrored lamps.

Chromium has good adhesion to nickel, copper, brass, and other deposited materials, but poor adhesion is always observed when other metals are deposited on chromium.

A positive feature of chromium coatings is that the parts are shiny directly in galvanic baths, this does not require them to be polished mechanically. Along with this, chromium plating differs from other galvanic processes by more stringent requirements for the operating mode of the baths. Minor deviations from the required current density, electrolyte temperature and other parameters inevitably lead to deterioration of coatings and mass rejects.

The scattering power of chromium electrolytes is low, which leads to poor coating of internal surfaces and recesses of parts. To improve the uniformity of coatings, special suspensions and additional screens are used.

For chromium plating, solutions of chromic anhydride with the addition of sulfuric acid are used.

Three types of electrolytes have found industrial application: diluted, universal and concentrated (Table 1). To obtain decorative coatings and to obtain reflectors, a concentrated electrolyte is used. In chromium plating, insoluble lead anodes are used.

Table 1 - Electrolyte compositions for chromium plating

During operation, the concentration of chromic anhydride in the baths decreases, therefore, to restore the baths, daily adjustments are made by adding fresh chromic anhydride to them.

Several formulations of self-regulating electrolytes have been developed, in which the concentration ratio is automatically stored

.

The composition of such an electrolyte is as follows, g/l:

Chrome plating is carried out at a cathode current density of 50–80 A/dm2 and a temperature of 60–70°C.

Depending on the relationship between temperature and current density, different types of chromium coating can be obtained: milky shiny and matte.

Chrome vs Nickel

When deciding what you choose for your home and business, it's always important to be sure of what you want to achieve. This is because, like clothes and shoes, trim also goes out of style. Recently, finishes such as chrome and nickel are very popular among households and even among businesses. These are two types of finishes that can easily adapt to modern appliances and equipment, whether in the kitchen, bathrooms or rooms. They give off an elegant and clean finish. Chrome and nickel have a silver tint. Therefore, before choosing what you want to use for the finish, it is always wise to look at how they differ from each other in the first place.

The chrome finish is very shiny, reflective and has a mirror finish. Some people also prefer this because it looks timeless and classy. It is popular not only in household lighting, but also in other uses such as fishing lures and the automotive industry. Not only is it attractive due to its silver hue, but it is also very durable. It does not corrode and can withstand intense temperature and weather. There is no such thing as hard chrome, but it is actually materials such as metal, copper, or steel that have been plated with chrome. There is a bit of a downside to the chrome finish. Thanks to their smooth, mirror-like surface, they easily show signs to the naked eye such as fingerprints, water stains, and even scratches. Despite this, chrome does not tarnish over time, unlike nickel which has a slightly cloudy tarnish.

Unlike the colder-toned chrome finish, the nickel finish has a warm and silver undertone. It was the standard finish in kitchens and bathrooms between the 1900s and 1930s. It is not shiny like chrome but has a rather dull or matte finish. Nickel also gives antique style. The upside to choosing a nickel plating is that due to its matte or dull finish, no marks or scratches will be an issue. It does not show fingerprints or watermarks, unlike the shiny ones. Also, nickel does not wear out easily, but it will tarnish over time. Despite this, it is very durable and can withstand extreme temperatures and humidity. Compared to chromium, nickel is also cheaper.

Both chrome and nickel have their advantages and disadvantages. A good way to decide what to use in between is to start and see what you want to finish already in the house. You also have to keep in mind that chrome is a bit more expensive than nickel, but a little more spending won't hurt if you want to achieve that shiny finish. You also have to consider if you are too detail oriented because shiny surfaces like chrome can support maintenance a bit due to the visibility of flaws compared to a dull nickel finish. Nickel finishes also tend to tarnish over time. However, they are both durable and don't wear out easily.

1.Chrome has a mirror finish and nickel has a brushed matte finish. 2. Both are durable and can withstand extreme temperatures. 3. Nickel may tarnish over time, but chrome will not. 4. Due to the shiny chrome finish, it can easily show imperfections such as fingerprints and scratches. Nickel, however, does not show these marks. 5. Chrome is slightly more expensive compared to nickel. 6. Due to the visibility of fingerprints or watermarks on chrome, a little more maintenance is required.

The presented training courses are to help beginners who love decorative chrome plating of chemical plating. The purpose of the training courses is to fill the gap of systematized knowledge on the topic of decorative chrome plating by chemical plating and make this technology more accessible to beginners. The presented texts, photos and videos are the author's personal experience, which does not claim to be professional. The author of the training courses is not responsible for possible injuries, burns and poisoning associated with the use of hazardous chemicals such as concentrated acids, alkalis, ammonia. Therefore, do not neglect protective equipment and care when handling reagents.

Decorative chrome plating, chemical plating, all these terms and processes were not known to me not so long ago. Dear friend, since you are on this site, it means that you are also hooked on this topic and you are looking for answers to questions. Questions that haunt you ... How to make any thing with a mirror shine? However, the answers are very close, just sit back and carefully look at the contents of this page. In fact, this is a technology of mirror silvering by spraying. This is also called chemical silver plating. So, there is no talk of real chrome plating, but the name has taken root and is misleading. When I started collecting information on this topic, I was faced with the fact that there is a lot of information on the topic of decorative chrome plating, but to my amazement, nothing specific. All around, yes. Here are a lot of videos where garage craftsmen, as well as pros selling equipment, are happy to demonstrate the process of transforming a nondescript detail into a product sparkling with a mirror. But step by step, all the technology, no one lays out for nothing, inflating a big, big secret out of it ... There are many questions, but the answers are paid ...

After reading a mountain of sites and textbooks, a mess formed in my head, probably, like many others, faced with such a task. So that a clear picture appeared in my head, I decided to immediately practice. It is clear that without chemistry, you will not learn how to chemistry, so I began to search and bypass the offices that sell chemistry. First of all, I asked the price for silver nitrate, since this is the most expensive component. Decide on a supplier. For bought on the list of chemicals, dishes and other necessary utensils. The question arose how to try without equipment. The solution is simple - manual household sprayers. The search and experiments began to create a miracle solution of silvering and application technology. And then one interesting detail about the preparation of chemistry emerged ... All the available information posted on the Internet is a copy of the materials of mainly Soviet textbooks on the topic of chemical metallization ...

Draining a fair amount of silver (respectively, money) to the ground in the process of unsuccessful experiments. Came for a pretty good recipe. In other words, everything is in order. This is the end of the lyrical introduction and the beginning of a short course on how to make a thing a mirror. I will not ship the theory, I will leave it for independent study. There is a lot of this goodness on the Internet. Let's get straight to the point. Short, concise, to the point. I will show you on the example of silvering a glass cup.

Technology of chemical metallization with silver, sputtering method

To get the first experience of silver coating on the surface, by spraying, you should learn the technology. And to put it simply - the sequence of actions.

I will list them:
1. preparation of solutions
2. surface preparation
3.surface activation
4. plating

I will give a brief overview of the above points. To get the big picture in my head. Let's take a closer look at the lessons of the same name.

Preparation of solutions

To prepare solutions you will need:

• stannous chloride
• Hydrochloric acid
• Nitrate silver
• Sodium hydroxide
• Ammonia
• Glucose
• Formalin
• Distilled water

We buy chemicals in stores or warehouses of medical equipment.

From the equipment you will need:

• Measuring cup for 1 liter
• Measuring cup for 200 - 250 ml.
• 100 ml bottles - 3 pcs.
• Disposable syringes for 5, 20 and 50 cubes
• Disposable cups 50 ml
• Disposable knives and spoons
• Electronic scales, measuring up to 200 gr.

We buy equipment in household goods and pharmacies.

You can start preparing solutions with a solution of tin dichloride. Required to activate the surface. For this we take:
1. Stannous chloride
2. Hydrochloric acid
3. Distilled water

The next solution is "silver". We take:
1. Nitrate silver
2. Sodium hydroxide
3. Ammonia
4. Distilled water

Surface preparation

To prepare the surface, it must be degreased. To do this, you can prepare a simple degreasing solution, consisting of:
1. Sodium hydroxide
2. and water temperature 40-60 degrees

The surface should be carefully wiped with a sponge moistened with a degreasing solution. Then wash off the solution with distilled water, wiping, but with another sponge. A sign of good degreasing is the wettability of the surface with water. That is, watering with water, the entire surface should be covered with a water film. If there are dry islands, silver will not stick there.

Surface activation

In order for the metallization reaction to occur precisely on the surface, and not in the drain, it is necessary to activate it, as they say. That is, to help the silver stick to the surface. It is for this that we take a solution of tin dichloride. The time of the procedure is very important here. Water the part with a solution of stannous chloride for one minute. Then pour with distilled water - three minutes. This is a very important stage and failure to comply with the surface treatment time leads to marriage, that is, to a waste of time, effort and money. Watering should be as even as possible so that all areas of the surface are equally moistened.

Metallization

This is the most interesting stage of obtaining a mirror film of silver on the surface. Actually for the sake of this, the whole idea. To do this, you need only a silver solution and a reducing agent solution. This will require some skill, which comes with experience. It is necessary to spray so that the solutions mix on the surface and nothing else. And sprayed in equal amounts by volume. Having reached such accuracy, we get an ideal mirror, without defects.

In addition, you should know that the resulting mirror film is not durable and in order for it to retain its properties, it should be protected with a layer of transparent or tinted varnish. But that's a completely different story.

The process of decorative chrome plating can be repeated even at home in the bathroom without buying expensive equipment at minimal cost. You can learn more about the technology by studying the email course Technology of decorative chrome plating and trying it in practice, it will allow you to decide whether it is worth moving further in this direction.

What does the email course "Technology of decorative chrome plating" consist of?

• Chemistry and equipment.
• Recipes and preparation of solutions for silvering.
• Surface preparation for silver application.
• Metallization

This knowledge and skills cost me more than 40 thousand rubles and several months of time. The information is provided to you free of charge, in a concise form and to the point, in the form of 5 short lessons. In order to receive an email course, leave a request by filling out the form located above, under the video. Enter your real name and email address, then click the "Submit Application" button. After that, you will be taken to a page with instructions to confirm your application. Read it carefully and then go to your mailbox. You should receive an email confirming your application. Click on the confirmation link, and almost immediately you will receive the first letter of the Decorative Chrome Technology course, where you will receive comprehensive information on how to start using the technology.

Chromium is a refractory, very hard metal with extraordinary resistance to corrosion. These unique qualities provided him with such a high demand in industry and construction.

The consumer is most often familiar not with chrome products, but with objects coated with a thin layer of metal. The dazzling mirror shine of such a coating is attractive in itself, but it also has a purely practical significance. Chrome is resistant to corrosion and is able to protect alloys and metals from rust.

And today we will answer questions about whether chromium is a metal or non-metal, and if it is a metal, then which one: black or non-ferrous, heavy or light. We will also tell you in what form chromium occurs in nature, and what are the differences between chromium and other similar metals.

To begin with, let's talk about what chromium looks like, what metals it contains, and what is the peculiarity of such a substance. Chromium is a typical silver-bluish metal, heavy, exceeds in density, and also belongs to the category of refractory - its melting and boiling points are very high.

The element chromium is placed in the secondary subgroup of the 6th group in the 4th period. It is close in properties to molybdenum and tungsten, although it also has noticeable differences. The latter most often exhibit only the highest oxidation state, while chromium exhibits a valence of two, three, and six. This means that the element forms many different compounds.

It was the compounds that gave the name to the element itself - from the Greek paint, color. The fact is that its salts and oxides are painted in a wide variety of bright colors.

This video will tell you what chrome is:

Features and differences compared to other metals

In the study of metal, two properties of a substance aroused the greatest interest: hardness and refractoriness. Chromium is one of the hardest metals - it ranks fifth and is inferior to uranium, iridium, tungsten and beryllium. However, this quality turned out to be unclaimed, since the metal had properties that were more important for industry.

Chromium melts at 1907 C. It is inferior to tungsten or molybdenum in this indicator, but still belongs to refractory substances. True, impurities strongly influence its melting point.

• Like many corrosion-resistant metals, chromium forms a thin and very dense oxide film in air. The latter covers the access of oxygen, nitrogen and moisture to the substance, which makes it invulnerable. The peculiarity is that he transfers this quality to his alloy with: in the presence of an element, the potential of the a-phase of iron increases and, as a result, steel in air is also covered with a dense oxide film. This is the secret to the durability of stainless steel.
• Being a refractory substance, the metal also increases the melting point of the alloy. Heat-resistant and heat-resistant steels necessarily include a proportion of chromium, and sometimes very large - up to 60%. The addition of both and chromium has an even stronger effect.
• Chromium forms alloys with its brothers in the group - molybdenum and tungsten. They are used for coating parts where particularly high wear resistance at high temperatures is required.

The advantages and disadvantages of chromium are described below.

Chrome as metal (photo)

Advantages

Like any other substance, metal has its advantages and disadvantages, and their combination determines its use.

• An unconditional plus of the substance is corrosion resistance and the ability to transfer this property to its alloys. Chromium stainless steels are of great importance because they have solved a number of problems in the construction of ships, submarines, building frames and so on at once.
• Corrosion resistance is provided in another way - they cover the object with a thin layer of metal. The popularity of this method is very high, today there are at least a dozen ways of chrome plating in different conditions and to obtain different results.
• The chrome layer creates a bright mirror shine, so chrome plating is used not only to protect the alloy from corrosion, but also to obtain an aesthetic appearance. Moreover, modern chromium plating methods make it possible to create a coating on any material - not only on metal, but also on plastic and ceramics.
• Obtaining heat-resistant steel with the addition of chromium should also be attributed to the advantages of the substance. There are many areas where metal parts must work at high temperatures, and iron itself does not have such resistance to stress at temperature.
• Of all the refractory substances, it is the most resistant to acids and bases.
• The advantage of the substance can be considered its prevalence - 0.02% in the earth's crust, and a relatively simple method of extraction and production. Of course, it requires energy consumption, but it cannot be compared with a complex one, for example.

disadvantages

The disadvantages include qualities that do not allow full use of all the properties of chromium.

• First of all, this is a strong dependence of physical, and not only chemical properties on impurities. Even the melting point of the metal was difficult to establish, since in the presence of an insignificant fraction of nitrogen or carbon, the indicator changed noticeably.
• Despite the higher electrical conductivity compared to, chromium is much less used in electrical engineering and its cost is quite high. It is much more difficult to make something from it: the high melting point and hardness significantly limit the application.
• Pure chromium is a malleable metal, containing impurities becomes very hard. To obtain at least a relatively ductile metal, it has to be subjected to additional processing, which, of course, increases the cost of manufacturing.

metal structure

The chromium crystal has a body-centered cubic lattice, a=0.28845 nm. Above a temperature of 1830 C, a modification with a face-centered cubic lattice can be obtained.

At a temperature of +38 C, a second-order phase transition is recorded with an increase in volume. In this case, the crystal lattice of the substance does not change, but its magnetic properties become completely different. Up to this temperature - the Neel point, chromium exhibits the properties of an antiferromagnet, that is, it is a substance that is almost impossible to magnetize. Above the Neel point, the metal becomes a typical paramagnet, that is, it exhibits magnetic properties in the presence of a magnetic field.

Properties and characteristics

Under normal conditions, the metal is quite inert - both due to the oxide film and simply by its nature. However, when the temperature rises, it reacts with simple substances, and with acids, and with bases. Its compounds are very diverse and are used very widely. The physical characteristics of the metal, as mentioned, strongly depend on the amount of impurities. In practice, they deal with chromium with a purity of up to 99.5%. are:

• melting temperature- 1907 C. This value serves as the boundary between refractory and ordinary substances;
• boiling temperature- 2671 C;
• Mohs hardness – 5;
• electrical conductivity– 9 106 1/(Ohm m). According to this indicator, chromium is second only to silver and gold;
• resistivity–127 (Ohm mm2)/m;
• thermal conductivity substances is 93.7 W / (m K);
• specific heat–45 J/(g K).

The thermophysical characteristics of the substance are somewhat anomalous. At the Neel point, where the volume of the metal changes, its coefficient of thermal expansion sharply increases and continues to grow with increasing temperature. The thermal conductivity also behaves abnormally - it drops at the Neel point and decreases when heated.

The element is among the necessary: ​​in the human body, chromium ions are participants in carbohydrate metabolism and the process of regulating insulin release. The daily dose is 50-200 mcg.

Chromium is non-toxic, although in the form of a metal powder it can cause irritation to the mucous membranes. Its trivalent compounds are also relatively safe and are even used in the food and sports industries. But hexavalent for humans are poison, cause severe damage to the respiratory tract and gastrointestinal tract.

We will talk further about the production and price of chromium metal per kg today.

This video will show if the finish is chrome:

Production

In a large number of different minerals - often accompanies and. However, its content is insufficient to be of industrial importance. Only rocks containing at least 40% of the element are promising, so there are few minerals suitable for extraction, mainly chromium iron ore or chromite.

The mineral is mined by the mine and quarry method, depending on the depth of occurrence. And since the ore initially contains a large proportion of the metal, it is almost never enriched, which, accordingly, simplifies and reduces the cost of the production process.

About 70% of the mined metal is used for alloying steel. Moreover, it is often used not in its pure form, but in the form of ferrochrome. The latter can be obtained directly in a shaft electric furnace or a blast furnace - this is how carbon ferrochromium is obtained. If a low carbon compound is required, the aluminothermic method is used.

• This method produces both pure chromium and ferrochrome. To do this, a charge is loaded into the smelting shaft, including chromium iron ore, chromium oxide, sodium nitrate and. The first portion, the ignition mixture, is ignited, and the rest of the charge is loaded into the melt. At the end, a flux is added - lime, to facilitate the extraction of chromium. Melting takes about 20 minutes. After some cooling, the shaft is tilted, slag is released, returned to its original position and tilted again, now both chromium and slag are removed into the mold. After cooling, the resulting block is separated.
• Another method is also used - metallothermic melting. It is carried out in an electric furnace in a rotating shaft. The charge here is divided into 3 parts, each differs in composition. This method allows you to extract more chromium, but, most importantly, it reduces consumption.
• If it is required to obtain a chemically pure metal, they resort to a laboratory method: crystals are planted by electrolysis of chromate solutions.

The cost of chromium metal per 1 kg fluctuates markedly, since it depends on the volume of rolled metal produced - the main consumer of the element. In January 2017, 1 ton of metal was valued at $7,655.

Application

Categories

So, . The main consumer of chromium is ferrous metallurgy. This is due to the ability of the metal to transfer its properties such as corrosion resistance and hardness to its alloys. Moreover, it has an effect when added in very small quantities.

All alloys of chromium and iron are divided into 2 categories:

• low-alloyed- with a share of chromium up to 1.6%. In this case, chromium adds strength and hardness to the steel. If ordinary steel has a tensile strength of 400–580 MPa, then the same steel grade with the addition of 1% of the substance will show a limit equal to 1000 MPa;
• highly alloyed- contain more than 12% chromium. Here, the metal provides the alloy with the same resistance to corrosion as it has on its own. All stainless steels are called chromium because it is this element that provides this quality.

Low-alloy steels are structural: they are used to make numerous machine parts - shafts, gears, pushers, and so on. The sphere of use of stainless steel is huge: metal parts of turbines, ship and submarine hulls, combustion chambers, fasteners of any kind, pipes, channels, angles, sheet steel, and so on.

In addition, chromium increases the resistance of the alloy to temperature: with a substance content of 30 to 66%, heat-resistant steel products can perform their functions when heated up to 1200 C. This is a material for piston engine valves, for fasteners, for turbine parts and other things.

If 70% of chromium goes to the needs of metallurgy, then the remaining almost 30% is used for chromium plating. The essence of the process is to apply a thin layer of chromium to the surface of a metal object. A variety of methods are used for this, many are available to home craftsmen.

Chrome plating

Chrome plating can be divided into 2 categories:

• functional- its purpose is to prevent corrosion of the product. The layer thickness is greater here, so the chrome plating process takes longer - sometimes up to 24 hours. In addition to the fact that the chromium layer will prevent rusting, it significantly increases the wear resistance of the part;
• decorative- Chrome creates a mirror-shiny surface. Car enthusiasts and motorcycle racers rarely turn down the opportunity to decorate their car with chrome parts. The decorative coating layer is much thinner - up to 0.0005 mm.

Chrome plating is actively used in modern construction and in the manufacture of furniture. Mirrored fittings, bathroom and kitchen accessories, kitchen utensils, furniture parts - chrome-plated products are extremely popular. And since, thanks to the modern chromium plating method, a coating can be created on literally any object, several atypical methods of application have also appeared. So, for example, chrome-plated plumbing cannot be attributed to trivial solutions.

Chromium is a metal with very unusual properties, and its qualities are in demand in industry. For the most part, its alloys and compounds are of interest, which only increases the importance of the metal for the national economy.

The video below will tell about the removal of chrome from metal:

Information for action
(technology tips)
Erlykin L.A. DIY 3-92

Before any of the home craftsmen did not get up the need to nickel or chrome this or that part. What do-it-yourselfer has not dreamed of installing a “failed” bushing with a hard, wear-resistant surface obtained by saturating it with boron in a critical node. But how to do at home what, as a rule, is carried out at specialized enterprises by methods of chemical-thermal and electrochemical processing of metals. You will not build gas and vacuum furnaces at home, or build electrolysis baths. But it turns out that it is not necessary to build all this at all. It is enough to have on hand some reagents, an enameled pan and, perhaps, a blowtorch, as well as to know the recipes of "chemical technology", with which metals can also be copper-plated, cadmium, tinned, oxidized, etc.

So, let's start getting acquainted with the secrets of chemical technology. Please note that the content of the components in the solutions given, as a rule, are given in g / l. If other units are used, a special clause follows.

Preparatory operations

Before applying paints, protective and decorative films to metal surfaces, as well as before coating them with other metals, it is necessary to carry out preparatory operations, that is, to remove contaminants of various nature from these surfaces. Please note that the final result of all work depends to a large extent on the quality of the preparatory operations.

Preparatory operations include degreasing, cleaning and pickling.

Degreasing

The process of degreasing the surface of metal parts is carried out, as a rule, when these parts have just been processed (ground or polished) and there are no rust, scale and other foreign products on their surface.

With the help of degreasing, oil and grease films are removed from the surface of the parts. For this, aqueous solutions of some chemicals are used, although organic solvents can also be used for this. The latter have the advantage that they do not have a subsequent corrosive effect on the surface of the parts, but they are toxic and flammable.

aqueous solutions. Degreasing of metal parts in aqueous solutions is carried out in enameled dishes. Pour water, dissolve chemicals in it and put on a small fire. When the desired temperature is reached, the parts are loaded into the solution. During processing, the solution is stirred. Below are the compositions of the degreasing solutions (g/l), as well as the operating temperatures of the solutions and the processing time of the parts.

Compositions of degreasing solutions (g/l)

For ferrous metals (iron and iron alloys)

Liquid glass (stationery silicate glue) - 3 ... 10, caustic soda (potassium) - 20 ... 30, trisodium phosphate - 25 ... 30. Solution temperature - 70...90°C, processing time - 10...30 min.

Liquid glass - 5 ... 10, caustic soda - 100 ... 150, soda ash - 30 ... 60. Solution temperature - 70...80°C, processing time - 5...10 min.

Liquid glass - 35, trisodium phosphate - 3 ... 10. Solution temperature - 70...90°С, processing time - 10...20 min.

Liquid glass - 35, trisodium phosphate - 15, preparation - emulsifier OP-7 (or OP-10) -2. Solution temperature - 60-70°С, processing time - 5...10 min.

Liquid glass - 15, preparation OP-7 (or OP-10) -1. Solution temperature - 70...80°С, processing time - 10...15 min.

Soda ash - 20, potassium chromium peak - 1. Solution temperature - 80 ... 90 ° C, processing time - 10 ... 20 minutes.

Soda ash - 5 ... 10, trisodium phosphate - 5 ... 10, preparation OP-7 (or OP-10) - 3. Solution temperature - 60 ... 80 ° C, processing time - 5 ... 10 min .

For copper and copper alloys

Caustic soda - 35, soda ash - 60, trisodium phosphate - 15, preparation OP-7 (or OP-10) - 5. Solution temperature - 60 ... 70, processing time - 10 ... 20 minutes.

Caustic soda (potassium) - 75, liquid glass - 20 Solution temperature - 80 ... 90 ° C, processing time - 40 ... 60 minutes.

Liquid glass - 10 ... 20, trisodium phosphate - 100. Solution temperature - 65 ... 80 C, processing time - 10 ... 60 minutes.

Liquid glass - 5 ... 10, soda ash - 20 ... 25, preparation OP-7 (or OP-10) - 5 ... 10. Solution temperature - 60...70°С, processing time - 5...10 min.

Trisodium phosphate - 80...100. Solution temperature - 80...90°С, processing time - 30...40 min.

For aluminum and its alloys

Liquid glass - 25...50, soda ash - 5...10, trisodium phosphate-5...10, preparation OP-7 (or OP-10) - 15...20 min.

Liquid glass - 20 ... 30, soda ash - 50 ... 60, trisodium phosphate - 50 ... 60. Solution temperature - 50…60°С, processing time - 3...5 min.

Soda ash - 20 ... 25, trisodium phosphate - 20 ... 25, preparation OP-7 (or OP-10) - 5 ... 7. Temperature - 70...80°С, processing time - 10...20 min.

For silver, nickel and their alloys

Liquid glass - 50, soda ash - 20, trisodium phosphate - 20, preparation OP-7 (or OP-10) - 2. Solution temperature - 70 ... 80 ° C, processing time - 5 ... 10 minutes.

Liquid glass - 25, soda ash - 5, trisodium phosphate - 10. Solution temperature - 75 ... 85 ° C, processing time - 15 ... 20 minutes.

For zinc

Liquid glass - 20 ... 25, caustic soda - 20 ... 25, soda ash - 20 ... 25. Solution temperature - 65...75°С, processing time - 5 min.

Liquid glass - 30...50, soda ash - 30..,50, kerosene - 30...50, preparation OP-7 (or OP-10) - 2...3. Solution temperature - 60-70°С, processing time - 1...2 min.

organic solvents

The most commonly used organic solvents are B-70 gasoline (or "lighter gasoline") and acetone. However, they have a significant drawback - they are easily flammable. Therefore, they have recently been replaced by non-flammable solvents such as trichlorethylene and perchlorethylene. Their dissolving power is much higher than that of gasoline and acetone. Moreover, these solvents can be fearlessly heated, which greatly accelerates the degreasing of metal parts.

Degreasing the surface of metal parts with organic solvents is carried out in the following sequence. The parts are loaded into a container with a solvent and incubated for 15 ... 20 minutes. Then the surface of the parts is wiped directly in the solvent with a brush. After such treatment, the surface of each part is carefully treated with a swab moistened with 25% ammonia (it is necessary to work with rubber gloves!).

All work on degreasing with organic solvents is carried out in a well-ventilated area.

cleaning

In this section, as an example, the decarbonization process of internal combustion engines will be considered. As you know, carbon deposits are asphalt-resinous substances that form hard-to-remove films on the working surfaces of engines. Removing carbon deposits is a rather difficult task, since the carbon film is inert and firmly adhered to the surface of the part.

Compositions of cleaning solutions (g/l)

For ferrous metals

Liquid glass - 1.5, soda ash - 33, caustic soda - 25, laundry soap - 8.5. Solution temperature - 80...90°C, processing time - Zh.

Caustic soda - 100, potassium dichromate - 5. Solution temperature - 80 ... 95 ° C, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, sodium bichromate - 5, laundry soap - 8, soda ash - 30. Solution temperature - 80 ... 95 ° C, processing time - up to 3 hours.

Caustic soda - 25, liquid glass - 10, laundry soap - 10, potash - 30. Solution temperature - 100 ° C, processing time - up to 6 hours.

For aluminum (duralumin) alloys

Liquid glass 8.5, laundry soap - 10, soda ash - 18.5. Solution temperature - 85...95 C, processing time - up to 3 hours.

Liquid glass - 8, potassium dichromate - 5, laundry soap - 10, soda ash - 20. Solution temperature - 85 ... 95 ° C, processing time - up to 3 hours.

Soda ash - 10, potassium dichromate - 5, laundry soap - 10. Solution temperature - 80 ... 95 ° C, processing time - up to 3 hours.

Etching

Etching (as a preparatory operation) allows you to remove contaminants (rust, scale and other corrosion products) firmly adhered to their surface from metal parts.

The main purpose of etching is the removal of corrosion products; while the base metal should not be etched. To prevent metal etching, special additives are introduced into the solutions. Good results are obtained by the use of small amounts of hexamethylenetetramine (urotropine). In all solutions for etching ferrous metals, add 1 tablet (0.5 g) of urotropine per 1 liter of solution. In the absence of urotropin, it is replaced with the same amount of dry alcohol (sold in sports stores as fuel for tourists).

In view of the fact that inorganic acids are used in recipes for etching, it is necessary to know their initial density (g / cm 3): nitric acid - 1.4, sulfuric acid - 1.84; hydrochloric acid - 1.19; phosphoric acid - 1.7; acetic acid - 1.05.

Compositions of solutions for etching

For ferrous metals

Sulfuric acid - 90...130, hydrochloric acid - 80...100. Solution temperature - 30...40°С, processing time - 0.5...1.0 h.

Sulfuric acid - 150...200. Solution temperature - 25...60°С, processing time - 0.5...1.0 h.

Hydrochloric acid - 200. Solution temperature - 30...35°С, processing time - 15...20 min.

Hydrochloric acid - 150 ... 200, formalin - 40 ... 50. Solution temperature 30...50°C, treatment time 15...25 min.

Nitric acid - 70...80, hydrochloric acid - 500...550. Solution temperature - 50°С, processing time - 3...5 min.

Nitric acid - 100, sulfuric acid - 50, hydrochloric acid - 150. Solution temperature - 85°C, processing time - 3...10 min.

Hydrochloric acid - 150, phosphoric acid - 100. Solution temperature - 50°C, processing time - 10...20 min.

The last solution (when processing steel parts), in addition to cleaning the surface, also phosphates it. And phosphate films on the surface of steel parts make it possible to paint them with any paint without a primer, since these films themselves serve as an excellent primer.

Here are a few more recipes for etching solutions, the compositions of which this time are given in% (by weight).

Orthophosphoric acid - 10, butyl alcohol - 83, water - 7. Solution temperature - 50...70°C, processing time - 20...30 min.

Orthophosphoric acid - 35, butyl alcohol - 5, water - 60. Solution temperature - 40...60°C, processing time - 30...35 min.

After etching of ferrous metals, they are washed in a 15% solution of soda ash (or drinking) soda. Then rinse thoroughly with water.

Note that below the compositions of the solutions are again given in g/l.

For copper and its alloys

Sulfuric acid - 25...40, chromic anhydride - 150...200. Solution temperature - 25°С, processing time - 5...10 min.

Sulfuric acid - 150, potassium bichromate - 50. Solution temperature - 25.35°C, processing time - 5...15 min.

Trilon B-100. Solution temperature - 18...25°C, processing time - 5...10 min.

Chromic anhydride - 350, sodium chloride - 50. Solution temperature - 18...25°С, processing time - 5...15 min.

For aluminum and its alloys

Caustic soda -50...100. Solution temperature - 40...60°С, treatment time - 5...10 s.

Nitric acid - 35...40. Solution temperature - 18...25°С, treatment time - 3...5 s.

Caustic soda - 25 ... 35, soda ash - 20 ... 30. Solution temperature - 40...60°С, treatment time - 0.5...2.0 min.

Caustic soda - 150, sodium chloride - 30. Solution temperature - 60°C, processing time - 15 ... 20 s.

Chemical polishing

Chemical polishing allows you to quickly and efficiently process the surface of metal parts. The great advantage of this technology is that with the help of it (and only it!) It is possible to polish parts with a complex profile at home.

Compositions of solutions for chemical polishing

For carbon steels (the content of components is indicated in each case in certain units (g / l, percent, parts)

Nitric acid - 2.-.4, hydrochloric acid 2 ... 5, Orthophosphoric acid - 15 ... 25, the rest is water. Solution temperature - 70...80°С, processing time - 1...10 min. The content of the components - in% (by volume).

Sulfuric acid - 0.1, acetic acid - 25, hydrogen peroxide (30%) - 13. Solution temperature - 18 ... 25 ° C, processing time - 30 ... 60 minutes. Content of components - in g/l.

Nitric acid - 100...200, sulfuric acid - 200..,600, hydrochloric acid - 25, Orthophosphoric acid - 400. Mixture temperature - 80...120°С, treatment time - 10...60 s. Content of components in parts (by volume).

For stainless steel

Sulfuric acid - 230, hydrochloric acid - 660, acid orange dye - 25. Solution temperature - 70...75°С, processing time - 2...3 min. Content of components - in g/l.

Nitric acid - 4 ... 5, hydrochloric acid - 3 ... 4, Orthophosphoric acid - 20..30, methyl orange - 1..1.5, the rest is water. Solution temperature - 18...25°С, treatment time - 5..10 min. The content of the components - in% (by weight).

Nitric acid - 30...90, potassium ferricyanide (yellow blood salt) - 2...15 g/l, preparation OP-7 - 3...25, hydrochloric acid - 45..110, phosphoric acid - 45. ..280.

Solution temperature - 30...40°С, processing time - 15...30 min. The content of components (except for yellow blood salt) - in pl / l.

The latter composition is applicable for polishing cast iron and any steels.

For copper

Nitric acid - 900, sodium chloride - 5, soot - 5. Solution temperature - 18 ... 25 ° C, processing time - 15 ... 20 s. Content of components - g/l.

Attention! Sodium chloride is added to solutions last, and the solution must be pre-cooled!

Nitric acid - 20, sulfuric acid - 80, hydrochloric acid - 1, chromic anhydride - 50. Solution temperature - 13..18°C, processing time - 1...2 min. Content of components - in ml.

Nitric acid 500, sulfuric acid - 250, sodium chloride - 10. Solution temperature - 18 ... 25 ° C, processing time - 10 ... 20 s. Content of components - in g/l.

For brass

Nitric acid - 20, hydrochloric acid - 0.01, acetic acid - 40, phosphoric acid - 40. Mixture temperature - 25...30°C, processing time - 20...60 s. Content of components - in ml.

Copper sulphate (copper sulfate) - 8, sodium chloride - 16, acetic acid - 3, water - the rest. Solution temperature - 20°С, processing time - 20...60 min. The content of components - in% (by weight).

For bronze

Orthophosphoric acid - 77 ... 79, potassium nitrate - 21 ... 23. Mixture temperature - 18°C, processing time - 0.5-3 min. The content of components - in% (by weight).

Nitric acid - 65, sodium chloride - 1 g, acetic acid - 5, orthophosphoric acid - 30, water - 5. Solution temperature - 18 ... 25 ° C, processing time - 1 ... 5 s. The content of components (except sodium chloride) - in ml.

For nickel and its alloys (cupronickel and nickel silver)

Nitric acid - 20, acetic acid - 40, phosphoric acid - 40. Mixture temperature - 20°C, processing time - up to 2 minutes. The content of components - in% (by weight).

Nitric acid - 30, acetic acid (glacial) - 70. Mixture temperature - 70...80°С, treatment time - 2...3 s. The content of components - in% (by volume).

For aluminum and its alloys

Orthophosphoric acid - 75, sulfuric acid - 25. Mixture temperature - 100°C, processing time - 5...10 min. The content of components - in parts (by volume).

Orthophosphoric acid - 60, sulfuric acid - 200, nitric acid - 150, urea - 5g. The temperature of the mixture is 100°C, the processing time is 20 s. The content of components (except urea) - in ml.

Orthophosphoric acid - 70, sulfuric acid - 22, boric acid - 8. Mixture temperature - 95°C, processing time - 5...7 min. The content of components - in parts (by volume).

Passivation

Passivation is the process of chemically creating an inert layer on the surface of a metal, which prevents the metal itself from oxidizing. The process of passivating the surface of metal products is used by chasers when creating their works; craftsmen - in the manufacture of various crafts (chandeliers, sconces and other household items); sports anglers passivate their homemade metal lures.

Compositions of solutions for passivation (g/l)

For ferrous metals

Sodium nitrite - 40...100. Solution temperature - 30...40°С, processing time - 15...20 min.

Sodium nitrite - 10...15, soda ash - 3...7. Solution temperature - 70...80°С, processing time - 2...3 min.

Sodium nitrite - 2...3, soda ash - 10, preparation OP-7 - 1...2. Solution temperature - 40...60°С, processing time - 10...15 min.

Chromic anhydride - 50. Solution temperature - 65 ... 75 "C, processing time - 10 ... 20 minutes.

For copper and its alloys

Sulfuric acid - 15, potassium dichromate - 100. Solution temperature - 45°C, processing time - 5...10 min.

Potassium dichromate - 150. Solution temperature - 60°C, processing time - 2...5 min.

For aluminum and its alloys

Orthophosphoric acid - 300, chromic anhydride - 15. Solution temperature - 18...25°C, processing time - 2...5 min.

Potassium dichromate - 200. Solution temperature - 20°C, "treatment time -5...10 min.

For silver

Potassium dichromate - 50. Solution temperature - 25 ... 40 ° C, processing time - 20 minutes.

For zinc

Sulfuric acid - 2...3, chromic anhydride - 150...200. Solution temperature - 20°С, processing time - 5...10 s.

Phosphating

As already mentioned, the phosphate film on the surface of steel parts is a fairly reliable anti-corrosion coating. It is also an excellent primer for paintwork.

Some low-temperature phosphating methods are applicable to the treatment of car bodies before coating them with anti-corrosion and anti-wear compounds.

Compositions of solutions for phosphating (g/l)

For steel

Mazhef (phosphate salts of manganese and iron) - 30, zinc nitrate - 40, sodium fluoride - 10. Solution temperature - 20 ° C, processing time - 40 minutes.

Monozinc phosphate - 75, zinc nitrate - 400 ... 600. Solution temperature - 20°С, processing time - 20...30 s.

Majef - 25, zinc nitrate - 35, sodium nitrite - 3. Solution temperature - 20°C, processing time - 40 min.

Monoammonium phosphate - 300. Solution temperature - 60 ... 80 ° C, processing time - 20 ... 30 s.

Phosphoric acid - 60...80, chromic anhydride - 100...150. Solution temperature - 50...60°С, processing time - 20...30 min.

Orthophosphoric acid - 400 ... 550, butyl alcohol - 30. Solution temperature - 50 ° C, processing time - 20 minutes.

Application of metal coatings

The chemical coating of some metals with others impresses with the simplicity of the technological process. Indeed, if, for example, it is necessary to chemically nickel-plating any steel part, it is enough to have suitable enameled dishes, a heating source (gas stove, stove, etc.) and relatively non-deficient chemicals. An hour or two - and the part is covered with a shiny layer of nickel.

Note that only with the help of chemical nickel plating it is possible to reliably nickel-plating parts of a complex profile, internal cavities (pipes, etc.). True, chemical nickel plating (and some other similar processes) is not without its drawbacks. The main one is not too strong adhesion of the nickel film to the base metal. However, this drawback can be eliminated; for this, the so-called low-temperature diffusion method is used. It allows you to significantly increase the adhesion of the nickel film to the base metal. This method is applicable to all chemical coatings of some metals by others.

nickel plating

The process of chemical nickel plating is based on the reaction of nickel reduction from aqueous solutions of its salts using sodium hypophosphite and some other chemicals.

Nickel coatings obtained by chemical means have an amorphous structure. The presence of phosphorus in nickel makes the film close in hardness to a chromium film. Unfortunately, the adhesion of the nickel film to the base metal is relatively low. Heat treatment of nickel films (low-temperature diffusion) consists in heating nickel-plated parts to a temperature of 400°C and keeping them at this temperature for 1 hour.

If nickel-plated parts are hardened (springs, knives, fish hooks, etc.), then at a temperature of 40 ° C they can be released, that is, they can lose their main quality - hardness. In this case, low-temperature diffusion is carried out at a temperature of 270...300 C with an exposure of up to 3 hours. In this case, the heat treatment also increases the hardness of the nickel coating.

All the listed advantages of chemical nickel plating did not escape the attention of technologists. They have found practical application for them (except for the use of decorative and anti-corrosion properties). So, with the help of chemical nickel plating, the axes of various mechanisms, worms of thread-cutting machines, etc. are repaired.

At home, with the help of nickel plating (of course, chemical!) You can repair parts of various household devices. The technology here is extremely simple. For example, the axis of a device was demolished. Then they build up (with excess) a layer of nickel on the damaged area. Then the working section of the axis is polished, bringing it to the desired size.

It should be noted that chemical nickel plating cannot cover metals such as tin, lead, cadmium, zinc, bismuth and antimony.
Solutions used for chemical nickel plating are divided into acidic (pH - 4 ... 6.5) and alkaline (pH - above 6.5). Acidic solutions are preferably used for coating ferrous metals, copper and brass. Alkaline - for stainless steels.

Acidic solutions (compared to alkaline ones) on a polished part give a smoother (mirror-like) surface, they have less porosity, and the speed of the process is higher. Another important feature of acidic solutions is that they are less likely to self-discharge when the operating temperature is exceeded. (Self-discharge - instantaneous precipitation of nickel into a solution with splashing of the latter.)

In alkaline solutions, the main advantage is a more reliable adhesion of the nickel film to the base metal.

And the last. Water for nickel plating (and when applying other coatings) is taken distilled (you can use condensate from household refrigerators). Chemical reagents are suitable at least pure (designation on the label - H).

Before coating parts with any metal film, it is necessary to conduct a special preparation of their surface.

Preparation of all metals and alloys is as follows. The treated part is degreased in one of the aqueous solutions, and then the part is decapitated in one of the solutions listed below.

Compositions of solutions for decapitation (g/l)

For steel

Sulfuric acid - 30...50. Solution temperature - 20°С, processing time - 20...60 s.

Hydrochloric acid - 20...45. Solution temperature - 20°С, treatment time - 15...40 s.

Sulfuric acid - 50...80, hydrochloric acid - 20...30. Solution temperature - 20°С, processing time - 8...10 s.

For copper and its alloys

Sulfuric acid - 5% solution. Temperature - 20°C, processing time - 20s.

For aluminum and its alloys

Nitric acid. (Attention, 10 ... 15% solution.) Solution temperature - 20 ° C, processing time - 5 ... 15 s.

Please note that for aluminum and its alloys, before chemical nickel plating, one more treatment is carried out - the so-called zincate. Below are solutions for zincate treatment.

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20 C, treatment time - 3 ... 5s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20 ° C, processing time - 1.5 ... 2 minutes.

When preparing both solutions, first, caustic soda is dissolved separately in half of the water, and the zinc component in the other half. Then both solutions are poured together.

For cast aluminum alloys

Caustic soda - 10, zinc oxide - 5, Rochelle salt (crystal hydrate) - 10. Solution temperature - 20 C, processing time - 2 minutes.

For wrought aluminum alloys

Ferric chloride (crystal hydrate) - 1, sodium hydroxide - 525, zinc oxide 100, Rochelle salt - 10. Solution temperature - 25 ° C, processing time - 30 ... 60 s.

After zincate treatment, the parts are washed in water and hung in a nickel plating solution.

All solutions for nickel plating are universal, that is, they are suitable for all metals (although there are some specifics). Prepare them in a certain sequence. So, all chemicals (except sodium hypophosphite) are dissolved in water (enamelled dishes!). Then the solution is heated to the operating temperature and only after that sodium hypophosphite is dissolved and the parts are hung into the solution.

In 1 liter of solution, a surface up to 2 dm2 in area can be nickel plated.

Compositions of solutions for nickel plating (g/l)

Nickel sulphate - 25, sodium succinic acid - 15, sodium hypophosphite - 30. Solution temperature - 90°C, pH - 4.5, film growth rate - 15...20 µm/h.

Nickel chloride - 25, sodium succinic acid - 15, sodium hypophosphite - 30. Solution temperature - 90 ... 92 ° C, pH - 5.5, growth rate - 18 ... 25 μm / h.

Nickel chloride - 30, glycolic acid - 39, sodium hypophosphite - 10. Solution temperature 85..89°С, pH - 4.2, growth rate - 15...20 µm/h.

Nickel chloride - 21, sodium acetate - 10, sodium hypophosphite - 24, Solution temperature - 97 ° C, pH - 5.2, growth rate - up to 60 μm / h.

Nickel sulfate - 21, sodium acetate - 10, lead sulfide - 20, sodium hypophosphite - 24. Solution temperature - 90 ° C, pH - 5, growth rate - up to 90 μm / h.

Nickel chloride - 30, acetic acid - 15, lead sulfide - 10 ... 15, sodium hypophosphite - 15. Solution temperature - 85 ... 87 ° C, pH - 4.5, growth rate - 12 ... 15 microns /h

Nickel chloride - 45, ammonium chloride - 45, sodium citrate - 45, sodium hypophosphite - 20. Solution temperature - 90 ° C, pH - 8.5, growth rate - 18 ... 20 microns / h.

Nickel chloride - 30, ammonium chloride - 30, sodium succinic acid - 100, ammonia (25% solution - 35, sodium hypophosphite - 25).
Temperature - 90°C, pH - 8...8.5, growth rate - 8...12 µm/h.

Nickel chloride - 45, ammonium chloride - 45, sodium acetate - 45, sodium hypophosphite - 20. Solution temperature - 88 .... 90 ° C, pH - 8 ... 9, growth rate - 18 ... 20 microns / h.

Nickel sulphate - 30, ammonium sulphate - 30, sodium hypophosphite - 10. Solution temperature - 85°C, pH - 8.2...8.5, growth rate - 15...18 µm/h.

Attention! According to existing state standards, a single-layer nickel coating per 1 cm2 has several tens of through (to the base metal) pores. Naturally, in the open air, a nickel-plated steel part will quickly become covered with a “rash” of rust.

In a modern car, for example, the bumper is covered with a double layer (a sublayer of copper, and chrome on top) and even a triple layer (copper - nickel - chrome). But even this does not save the part from rust, since according to GOST and the triple coating has several pores per 1 cm2. What to do? The way out is in the surface treatment of the coating with special compounds that close the pores.

Wipe the part with a nickel (or other) coating with a slurry of magnesium oxide and water and immediately lower it for 1 ... 2 minutes in a 50% hydrochloric acid solution.

After heat treatment, lower the part that has not yet cooled down into non-vitaminized fish oil (preferably old, unsuitable for its intended purpose).

Wipe the nickel-plated surface of the part 2...3 times with the composition of LPS (easy penetrating lubricant).

In the last two cases, excess fat (grease) is removed from the surface with gasoline in a day.

The treatment of large surfaces (bumpers, car moldings) with fish oil is carried out as follows. In hot weather, wipe them with fish oil twice with a break of 12-14 hours. Then, after 2 days, excess fat is removed with gasoline.

The effectiveness of such processing is characterized by the following example. Nickel-plated fishing hooks begin to rust immediately after the first sea fishing. The same hooks treated with fish oil do not corrode for almost the entire summer sea fishing season.

Chrome plating

Chemical chromium plating allows you to get a gray coating on the surface of metal parts, which, after polishing, acquires the desired shine. Chrome adheres well to nickel plating. The presence of phosphorus in chemically produced chromium greatly increases its hardness. Heat treatment for chrome plating is necessary.

Below are proven recipes for chemical chromium plating.

Compositions of solutions for chemical chromium plating (g/l)

Chromium fluoride - 14, sodium citrate - 7, acetic acid - 10 ml, sodium hypophosphite - 7. Solution temperature - 85 ... 90 ° C, pH - 8 ... 11, growth rate - 1.0 ... 2 .5 µm/h.

Chromium fluoride - 16, chromium chloride - 1, sodium acetate - 10, sodium oxalate - 4.5, sodium hypophosphite - 10. Solution temperature - 75 ... 90 ° C, pH - 4 ... 6, growth rate - 2 ...2.5 µm/h.

Chromium fluoride - 17, chromium chloride - 1.2, sodium citrate - 8.5, sodium hypophosphite - 8.5. Solution temperature - 85...90°C, pH - 8...11, growth rate - 1...2.5 µm/h.

Chromium acetate - 30, nickel acetate - 1, sodium glycolate - 40, sodium acetate - 20, sodium citrate - 40, acetic acid - 14 ml, sodium hydroxide - 14, sodium hypophosphite - 15. Solution temperature - 99 ° C, pH - 4...6, growth rate - up to 2.5 µm/h.

Chromium fluoride - 5 ... 10, chromium chloride - 5 ... 10, sodium citrate - 20 ... 30, sodium pyrophosphate (replacing sodium hypophosphite) - 50 ... 75.
Solution temperature - 100°C, pH - 7.5...9, growth rate - 2...2.5 µm/h.

Boronickel plating

The film of this dual alloy has increased hardness (especially after heat treatment), high melting point, high wear resistance and significant corrosion resistance. All this allows the use of such a coating in various responsible home-made structures. Below are the recipes for solutions in which boronickeling is carried out.

Compositions of solutions for chemical boron nickel plating (g/l)

Nickel chloride - 20, sodium hydroxide - 40, ammonia (25% solution): - 11, sodium borohydride - 0.7, ethylenediamine (98% solution) - 4.5. Solution temperature - 97°C, growth rate - 10 µm/h.

Nickel sulfate - 30, triethylsyntetramine - 0.9, sodium hydroxide - 40, ammonia (25% solution) - 13, sodium borohydride - 1. Solution temperature - 97 C, growth rate - 2.5 μm / h.

Nickel chloride - 20, sodium hydroxide - 40, Rochelle salt - 65, ammonia (25% solution) - 13, sodium borohydride - 0.7. Solution temperature - 97°C, growth rate - 1.5 µm/h.

Caustic soda - 4 ... 40, potassium metabisulphite - 1 ... 1.5, potassium sodium tartrate - 30 ... 35, nickel chloride - 10 ... 30, ethylenediamine (50% solution) - 10 ... 30 , sodium borohydride - 0.6 ... 1.2. Solution temperature - 40...60°C, growth rate - up to 30 µm/h.

Solutions are prepared in the same way as for nickel plating: first, everything except sodium borohydride is dissolved, the solution is heated and sodium borohydride is dissolved.

Borocobalting

The use of this chemical process makes it possible to obtain a film of particularly high hardness. It is used to repair friction pairs, where increased wear resistance of the coating is required.

Compositions of solutions for boron cobalt treatment (g/l)

Cobalt chloride - 20, sodium hydroxide - 40, sodium citrate - 100, ethylenediamine - 60, ammonium chloride - 10, sodium borohydride - 1. Solution temperature - 60 ° C, pH - 14, growth rate - 1.5 .. .2.5 µm/h.

Cobalt acetate - 19, ammonia (25% solution) - 250, potassium tartrate - 56, sodium borohydride - 8.3. Solution temperature - 50°С, pH - 12.5, growth rate - 3 µm/h.

Cobalt sulphate - 180, boric acid - 25, dimethylborazan - 37. Solution temperature - 18°C, pH - 4, growth rate - 6 µm/h.

Cobalt chloride - 24, ethylenediamine - 24, dimethylborazan - 3.5. Solution temperature - 70 C, pH - 11, growth rate - 1 µm/h.

The solution is prepared in the same way as boronickel.

Cadmium plating

On the farm, it is often necessary to use fasteners coated with cadmium. This is especially true for parts that are operated outdoors.

It is noted that chemically obtained cadmium coatings adhere well to the base metal even without heat treatment.

Cadmium chloride - 50, ethylenediamine - 100. Cadmium should be in contact with parts (suspension on cadmium wire, small parts are sprinkled with cadmium powder). Solution temperature - 65°C, pH - 6...9, growth rate - 4 µm/h.

Attention! Ethylenediamine is dissolved last in the solution (after heating).

copper plating

Chemical copper plating is most often used in the manufacture of printed circuit boards for radio electronics, in electroforming, for metallizing plastics, for double coating some metals with others.

Compositions of solutions for copper plating (g/l)

Copper sulphate - 10, sulfuric acid - 10. Solution temperature - 15...25°C, growth rate - 10 µm/h.

Potassium-sodium tartrate - 150, copper sulphate - 30, caustic soda - 80. Solution temperature - 15 ... 25 ° C, growth rate - 12 μm / h.

Copper sulphate - 10 ... 50, caustic soda - 10 ... 30, Rochelle salt 40 ... 70, formalin (40% solution) - 15 ... 25. Solution temperature - 20°C, growth rate - 10 µm/h.

Sulfuric copper - 8...50, sulfuric acid - 8...50. Solution temperature - 20°C, growth rate - 8 µm/h.

Copper sulphate - 63, potassium tartrate - 115, sodium carbonate - 143. Solution temperature - 20 C, growth rate - 15 µm/h.

Copper sulphate - 80 ... 100, caustic soda - 80 ..., 100, sodium carbonate - 25 ... 30, nickel chloride - 2 ... 4, Rochelle salt - 150 ... 180, formalin (40% - solution) - 30...35. Solution temperature - 20°C, growth rate - 10 µm/h. This solution makes it possible to obtain films with a low nickel content.

Copper sulfate - 25 ... 35, sodium hydroxide - 30 ... 40, sodium carbonate - 20-30, trilon B - 80 ... 90, formalin (40% solution) - 20 ... 25, rhodanine - 0.003 ... 0.005, potassium ferricyanide (red blood salt) - 0.1..0.15. Solution temperature - 18...25°C, growth rate - 8 µm/h.

This solution is highly stable over time and makes it possible to obtain thick copper films.

To improve the adhesion of the film to the base metal, heat treatment is the same as for nickel.

Silvering

Silver plating of metal surfaces is perhaps the most popular process among craftsmen, which they use in their work. Dozens of examples could be given. For example, restoration of the silver layer on cupronickel cutlery, silvering of samovars and other household items.

For chasers, silvering, together with chemical coloring of metal surfaces (it will be discussed below), is a way to increase the artistic value of chased paintings. Imagine a minted ancient warrior with silver plated chain mail and a helmet.

The process of chemical silvering can be carried out using solutions and pastes. The latter is preferable when processing large surfaces (for example, when silvering samovars or parts of large chased paintings).

Composition of solutions for silvering (g/l)

Silver chloride - 7.5, potassium ferricyanide - 120, potassium carbonate - 80. The temperature of the working solution is about 100 ° C. Processing time - until the desired thickness of the silver layer is obtained.

Silver chloride - 10, sodium chloride - 20, acid potassium tartrate - 20. Processing - in a boiling solution.

Silver chloride - 20, potassium ferricyanide - 100, potassium carbonate - 100, ammonia (30% solution) - 100, sodium chloride - 40. Processing - in a boiling solution.

First, a paste is prepared from silver chloride - 30 g, tartaric acid - 250 g, sodium chloride - 1250, and everything is diluted with water to the density of sour cream. 10 ... 15 g of paste is dissolved in 1 liter of boiling water. Processing - in a boiling solution.

Details are hung in solutions for silvering on zinc wires (strips).

The processing time is determined visually. It should be noted here that brass is better silvered than copper. On the latter, it is necessary to apply a rather thick layer of silver so that dark copper does not shine through the coating layer.

One more note. Solutions with silver salts cannot be stored for a long time, as explosive components can be formed in this case. The same applies to all liquid pastes.

Compositions of pastes for silvering.

2 g of lapis pencil is dissolved in 300 ml of warm water (sold in pharmacies, it is a mixture of silver nitrate and amino acid potassium, taken in a ratio of 1: 2 (by weight). A 10% sodium chloride solution is gradually added to the resulting solution until it stops The curdled precipitate of silver chloride is filtered off and thoroughly washed in 5-6 waters.

Dissolve 20 g of sodium thiosulfite in 100 ml of water. Silver chloride is added to the resulting solution until it no longer dissolves. The solution is filtered and tooth powder is added to it to the consistency of liquid sour cream. This paste is rubbed (silvered) with a cotton swab.

Lapis pencil - 15, citric acid (food) - 55, ammonium chloride - 30. Each component is ground into powder before mixing. The content of components - in% (by weight).

Silver chloride - 3, sodium chloride - 3, sodium carbonate - 6, chalk - 2. The content of components - in parts (by weight).

Silver chloride - 3, sodium chloride - 8, potassium tartrate - 8, chalk - 4. Content of components - in parts (by weight).

Silver nitrate - 1, sodium chloride - 2. Content of components - in parts (by weight).

The last four pastes are used as follows. Finely divided components are mixed. With a wet swab, powdering it with a dry mixture of chemicals, they rub (silver) the desired part. The mixture is added all the time, constantly moistening the swab.

When silvering aluminum and its alloys, the parts are first galvanized and then coated with silver.

Zincate treatment is carried out in one of the following solutions.

Compositions of solutions for zincate treatment (g/l)

For aluminum

Caustic soda - 250, zinc oxide - 55. Solution temperature - 20°C, treatment time - 3...5 s.

Caustic soda - 120, zinc sulfate - 40. Solution temperature - 20°C, processing time - 1.5...2.0 min. To obtain a solution, first caustic soda is dissolved in one half of the water, and zinc sulfate is dissolved in the other. Then both solutions are poured together.

For duralumin

Caustic soda - 10, zinc oxide - 5, Rochelle salt - 10. Solution temperature - 20°C, processing time - 1...2 min.

After zincate treatment, the parts are silvered in any of the above solutions. However, the following solutions (g / l) are considered the best.

Silver nitrate - 100, ammonium fluoride - 100. Solution temperature - 20°C.

Silver fluoride - 100, ammonium nitrate - 100. Solution temperature - 20°C.

Tinning

Chemical tinning of surfaces of parts is used as an anti-corrosion coating and as a preliminary process (for aluminum and its alloys) before soft soldering. Below are compositions for tinning some metals.

Compositions for tinning (g/l)

For steel

Stannous chloride (fused) - 1, ammonia alum - 15. Tinning is carried out in a boiling solution, the growth rate is 5 ... 8 microns / h.

Tin chloride - 10, aluminum-ammonium sulphate - 300. Tinning is carried out in a boiling solution, the growth rate is 5 microns / h.

Stannous chloride - 20, Rochelle salt - 10. Solution temperature - 80°C, growth rate - 3...5 µm/h.

Stannous chloride - 3 ... 4, Rochelle salt - until saturation. Solution temperature - 90...100°С, growth rate - 4...7 µm/h.

For copper and its alloys

Stannous chloride - 1, potassium tartrate - 10. Tinning is carried out in a boiling solution, the growth rate is 10 μm / h.

Stannous chloride - 20, sodium lactate - 200. Solution temperature - 20°C, growth rate - 10 µm/h.

Stannous chloride - 8, thiourea - 40...45, sulfuric acid - 30...40. Solution temperature - 20°C, growth rate - 15 µm/h.

Stannous chloride - 8...20, thiourea - 80...90, hydrochloric acid - 6.5...7.5, sodium chloride - 70...80. Solution temperature - 50...100°C, growth rate - 8 µm/h.

Stannous chloride - 5.5, thiourea - 50, tartaric acid - 35. Solution temperature - 60 ... 70 ° C, growth rate - 5 ... 7 μm / h.

When tinning parts made of copper and its alloys, they are hung on zinc pendants. Small parts are “powdered” with zinc filings.

For aluminum and its alloys

The tinning of aluminum and its alloys is preceded by some additional processes. First, the parts degreased with acetone or gasoline B-70 are treated for 5 minutes at a temperature of 70 ° C of the following composition (g / l): sodium carbonate - 56, sodium phosphate - 56. Then the parts are lowered for 30 s into a 50% solution of nitric acid, rinse thoroughly under running water and immediately place in one of the solutions (for tinning) below.

Sodium stannate - 30, sodium hydroxide - 20. Solution temperature - 50...60°C, growth rate - 4 µm/h.

Sodium stannate - 20 ... 80, potassium pyrophosphate - 30 ... 120, sodium hydroxide - 1.5..L, 7, ammonium oxalate - 10 ... 20. Solution temperature - 20...40°C, growth rate - 5 µm/h.

Removal of metal coatings

Usually this process is necessary to remove low-quality metal films or to clean any metal product being restored.

All of the following solutions work faster at elevated temperatures.

Compositions of solutions for removing metal coatings in parts (by volume)

For steel removing nickel from steel

Nitric acid - 2, sulfuric acid - 1, iron sulphate (oxide) - 5 ... 10. The temperature of the mixture is 20°C.

Nitric acid - 8, water - 2. Solution temperature - 20 C.

Nitric acid - 7, acetic acid (glacial) - 3. Mixture temperature - 30°C.

For removing nickel from copper and its alloys (g/l)

Nitrobenzoic acid - 40 ... 75, sulfuric acid - 180. Solution temperature - 80 ... 90 C.

Nitrobenzoic acid - 35, ethylenediamine - 65, thiourea - 5...7. Solution temperature - 20...80°C.

Technical nitric acid is used to remove nickel from aluminum and its alloys. The temperature of the acid is 50°C.

For removing copper from steel

Nitrobenzoic acid - 90, diethylenetriamine - 150, ammonium chloride - 50. Solution temperature - 80°C.

Sodium pyrosulfate - 70, ammonia (25% solution) - 330. Solution temperature - 60 °.

Sulfuric acid - 50, chromic anhydride - 500. Solution temperature - 20°C.

For removing copper from aluminum and its alloys (zinc finish)

Chromic anhydride - 480, sulfuric acid - 40. Solution temperature - 20...70°C.

Technical nitric acid. The temperature of the solution is 50°C.

For removing silver from steel

Nitric acid - 50, sulfuric acid - 850. Temperature - 80°C.

Nitric acid technical. Temperature - 20°C.

Silver is removed from copper and its alloys with technical nitric acid. Temperature - 20°C.

Chrome is removed from steel with a solution of caustic soda (200 g/l). Solution temperature - 20 C.

Chromium is removed from copper and its alloys with 10% hydrochloric acid. The temperature of the solution is 20°C.

Zinc is removed from steel with 10% hydrochloric acid - 200 g / l. The temperature of the solution is 20°C.

Zinc is removed from copper and its alloys with concentrated sulfuric acid. Temperature - 20 C.

Cadmium and zinc are removed from any metals with a solution of aluminum nitrate (120 g/l). The temperature of the solution is 20°C.

Tin from steel is removed with a solution containing sodium hydroxide - 120, nitrobenzoic acid - 30. The temperature of the solution is 20°C.

Tin is removed from copper and its alloys in a solution of ferric chloride - 75 ... 100, copper sulfate - 135 ... 160, acetic acid (glacial) - 175. The temperature of the solution is 20 ° C.

Chemical oxidation and coloring of metals

Chemical oxidation and coloring of the surface of metal parts are intended to create an anti-corrosion coating on the surface of the parts and enhance the decorative effect of the coating.

In ancient times, people already knew how to oxidize their crafts, changing their color (silver blackening, gold coloring, etc.), burn steel objects (heating a steel part to 220 ... 325 ° C, they lubricated it with hemp oil).

Compositions of solutions for oxidation and coloring of steel (g/l)

Note that before oxidation, the part is ground or polished, degreased and decapitated.

Black color

Caustic soda - 750, sodium nitrate - 175. Solution temperature - 135°C, processing time - 90 minutes. The film is dense, shiny.

Caustic soda - 500, sodium nitrate - 500. Solution temperature - 140°C, processing time - 9 minutes. The film is intense.

Caustic soda - 1500, sodium nitrate - 30. Solution temperature - 150°C, processing time - 10 min. The film is matte.

Caustic soda - 750, sodium nitrate - 225, sodium nitrite - 60. Solution temperature - 140 ° C, processing time - 90 minutes. The film is shiny.

Calcium nitrate - 30, phosphoric acid - 1, manganese peroxide - 1. Solution temperature - 100°C, processing time - 45 min. The film is matte.

All of the above methods are characterized by a high working temperature of the solutions, which, of course, does not allow processing large parts. However, there is one "low-temperature solution" suitable for this business (g / l): sodium thiosulfate - 80, ammonium chloride - 60, phosphoric acid - 7, nitric acid - 3. Solution temperature - 20 ° C, processing time - 60 minutes . The film is black, matte.

After oxidation (blackening) of steel parts, they are treated for 15 minutes in a solution of potassium chromium peak (120 g/l) at a temperature of 60°C.

Then the parts are washed, dried and coated with any neutral machine oil.

Blue

Hydrochloric acid - 30, ferric chloride - 30, mercury nitrate - 30, ethyl alcohol - 120. Solution temperature - 20 ... 25 ° C, processing time - up to 12 hours.

Sodium hydrosulphide - 120, lead acetate - 30. Solution temperature - 90...100°C, processing time - 20...30 min.

Blue color

Lead acetate - 15 ... 20, sodium thiosulfate - 60, acetic acid (glacial) - 15 ... 30. The temperature of the solution is 80°C. The processing time depends on the intensity of the color.

Compositions of solutions for oxidation and coloring of copper (g/l)

bluish black colors

Caustic soda - 600 ... 650, sodium nitrate - 100 ... 200. Solution temperature - 140°C, processing time - 2 hours.

Caustic soda - 550, sodium nitrite - 150 ... 200. Solution temperature - 135...140°С, processing time - 15...40 min.

Caustic soda - 700...800, sodium nitrate - 200...250, sodium nitrite -50...70. Solution temperature - 140...150°С, processing time - 15...60 min.

Caustic soda - 50 ... 60, potassium persulfate - 14 ... 16. Solution temperature - 60...65 C, processing time - 5...8 min.

Potassium sulfide - 150. Solution temperature - 30°C, processing time - 5...7 min.

In addition to the above, a solution of the so-called sulfuric liver is used. Sulfur liver is obtained by fusing in an iron can for 10 ... 15 minutes (with stirring) 1 part (by weight) of sulfur with 2 parts of potassium carbonate (potash). The latter can be replaced by the same amount of sodium carbonate or caustic soda.

The glassy mass of sulfuric liver is poured onto an iron sheet, cooled and crushed to a powder. Store sulfur liver in an airtight container.

A solution of sulfuric liver is prepared in an enamel bowl at the rate of 30...150 g/l, the temperature of the solution is 25...100°C, the processing time is determined visually.

With a solution of sulfuric liver, in addition to copper, silver can be well blackened and steel satisfactorily.

Green color

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 15...25°C. The color intensity is determined visually.

Brown color

Potassium chloride - 45, nickel sulphate - 20, copper sulphate - 100. Solution temperature - 90...100°C, color intensity is determined visually.

Brownish yellow color

Caustic soda - 50, potassium persulfate - 8. Solution temperature - 100°C, processing time - 5...20 min.

Blue

Sodium thiosulfate - 160, lead acetate - 40. Solution temperature - 40 ... 100 ° C, processing time - up to 10 minutes.

Compositions for oxidation and coloring of brass (g/l)

Black color

Copper carbonate - 200, ammonia (25% solution) - 100. Solution temperature - 30 ... 40 ° C, processing time - 2 ... 5 minutes.

Copper bicarbonate - 60, ammonia (25% solution) - 500, brass (sawdust) - 0.5. Solution temperature - 60...80°С, processing time - up to 30 min.

Brown color

Potassium chloride - 45, nickel sulfate - 20, copper sulfate - 105. Solution temperature - 90 ... 100 ° C, processing time - up to 10 minutes.

Copper sulphate - 50, sodium thiosulfate - 50. Solution temperature - 60 ... 80 ° C, processing time - up to 20 minutes.

Sodium sulfate - 100. Solution temperature - 70°C, processing time - up to 20 minutes.

Copper sulphate - 50, potassium permanganate - 5. Solution temperature - 18 ... 25 ° C, processing time - up to 60 minutes.

Blue

Lead acetate - 20, sodium thiosulfate - 60, acetic acid (essence) - 30. Solution temperature - 80 ° C, processing time - 7 minutes.

3 green color

Nickel ammonium sulphate - 60, sodium thiosulfate - 60. Solution temperature - 70 ... 75 ° C, processing time - up to 20 minutes.

Copper nitrate - 200, ammonia (25% solution) - 300, ammonium chloride - 400, sodium acetate - 400. Solution temperature - 20 ° C, processing time - up to 60 minutes.

Compositions for oxidation and coloring of bronze (g/l)

Green color

Ammonium chloride - 30, 5% acetic acid - 15, medium acetic copper salt - 5. Solution temperature - 25...40°C. Hereinafter, the color intensity of bronze is determined visually.

Ammonium chloride - 16, acidic potassium oxalate - 4, 5% acetic acid - 1. Solution temperature - 25...60°C.

Copper nitrate - 10, ammonium chloride - 10, zinc chloride - 10. Solution temperature - 18...25°C.

yellow green color

Nitrate copper - 200, sodium chloride - 20. Solution temperature - 25°C.

Blue to yellow-green

Depending on the processing time, it is possible to obtain colors from blue to yellow-green in a solution containing ammonium carbonate - 250, ammonium chloride - 250. The temperature of the solution is 18 ... 25 ° C.

Patination (giving the appearance of old bronze) is carried out in the following solution: sulfuric liver - 25, ammonia (25% solution) - 10. Solution temperature - 18 ... 25 ° C.

Compositions for oxidation and coloring of silver (g/l)

Black color

Sulfuric liver - 20...80. Solution temperature - 60..70°С. Hereinafter, the color intensity is determined visually.

Ammonium carbonate - 10, potassium sulfide - 25. Solution temperature - 40...60°C.

Potassium sulphate - 10. Solution temperature - 60°C.

Copper sulphate - 2, ammonium nitrate - 1, ammonia (5% solution) - 2, acetic acid (essence) - 10. Solution temperature - 25...40°C. The content of the components in this solution is given in parts (by weight).

Brown color

A solution of ammonium sulphate - 20 g / l. Solution temperature - 60...80°С.

Copper sulphate - 10, ammonia (5% solution) - 5, acetic acid - 100. Solution temperature - 30...60°C. The content of the components in the solution - in parts (by weight).

Copper sulphate - 100, 5% acetic acid - 100, ammonium chloride - 5. Solution temperature - 40...60°C. The content of the components in the solution - in parts (by weight).

Copper sulphate - 20, potassium nitrate - 10, ammonium chloride - 20, 5% acetic acid - 100. Solution temperature - 25...40°C. The content of the components in the solution - in parts (by weight).

Blue

Sulfuric liver - 1.5, ammonium carbonate - 10. Solution temperature - 60°C.

Sulfuric liver - 15, ammonium chloride - 40. Solution temperature - 40...60°C.

Green color

Iodine - 100, hydrochloric acid - 300. Solution temperature - 20°C.

Iodine - 11.5, potassium iodide - 11.5. The temperature of the solution is 20°C.

Attention! When dyeing silver green, you must work in the dark!

Composition for oxidation and coloring of nickel (g/l)

Nickel can only be painted black. The solution (g/l) contains: ammonium persulfate - 200, sodium sulfate - 100, iron sulfate - 9, ammonium thiocyanate - 6. Solution temperature - 20...25°C, processing time - 1-2 minutes.

Compositions for the oxidation of aluminum and its alloys (g/l)

Black color

Ammonium molybdate - 10...20, ammonium chloride - 5...15. Solution temperature - 90...100°С, treatment time - 2...10 min.

Grey colour

Arsenic trioxide - 70...75, sodium carbonate - 70...75. Solution temperature - boiling, processing time - 1...2 min.

Green color

Orthophosphoric acid - 40 ... 50, acidic potassium fluoride - 3 ... 5, chromic anhydride - 5 ... 7. Solution temperature - 20...40 C, processing time - 5...7 min.

Orange color

Chromic anhydride - 3...5, sodium fluorine silicate - 3...5. Solution temperature - 20...40°С, processing time - 8...10 min.

tan color

Sodium carbonate - 40 ... 50, sodium chlorate - 10 ... 15, caustic soda - 2 ... 2.5. Solution temperature - 80...100°С, processing time - 3...20 min.

Protective compounds

Often, the craftsman needs to process (paint, cover with another metal, etc.) only part of the craft, and leave the rest of the surface unchanged.
To do this, the surface that does not need to be covered is painted over with a protective compound that prevents the formation of a particular film.

The most accessible, but non-heat-resistant protective coatings are waxy substances (wax, stearin, paraffin, ceresin) dissolved in turpentine. To prepare such a coating, wax and turpentine are usually mixed in a ratio of 2: 9 (by weight). Prepare this composition as follows. Wax is melted in a water bath and warm turpentine is introduced into it. In order for the protective composition to be contrasting (its presence could be clearly seen, controlled), a small amount of dark-colored paint soluble in alcohol is introduced into the composition. If this is not available, it is easy to introduce a small amount of dark shoe cream into the composition.

You can give a recipe that is more complex in composition,% (by weight): paraffin - 70, beeswax - 10, rosin - 10, pitch varnish (Kuzbasslak) - 10. All components are mixed, melted over low heat and mixed thoroughly.

Wax-like protective compounds are applied hot with a brush or swab. All of them are designed for operating temperatures up to 70°C.
Somewhat better heat resistance (operating temperature up to 85°С) is possessed by protective compositions based on asphalt, bituminous and pitch varnishes. Usually they are thinned with turpentine in a ratio of 1:1 (by weight). The cold composition is applied to the surface of the part with a brush or swab. Drying time - 12...16 hours.

Perchlorovinyl paints, varnishes and enamels withstand temperatures up to 95°C, oil-bitumen varnishes and enamels, asphalt-oil and bakelite varnishes - up to 120°C.

The most acid-resistant protective composition is a mixture of 88N glue (or Moment) and filler (porcelain flour, talc, kaolin, chromium oxide), taken in the ratio: 1:1 (by weight). The required viscosity is obtained by adding to the mixture a solvent consisting of 2 parts (by volume) of B-70 gasoline and 1 part of ethyl acetate (or butyl acetate). The working temperature of such a protective composition is up to 150 C.

A good protective composition is epoxy varnish (or putty). Operating temperature - up to 160°С.