The weak point of metal pipes is susceptibility to corrosion. Over time, cast iron and steel pipes inevitably rust, and this affects the performance of the pipeline in a bad way. In order for the pipeline to serve longer and its condition not adversely affect water quality, rust should be removed in a timely manner.

Rust affects not only the fact that in places of formed plaque, the pipe can simply leak, but also the quality of the transported liquid. Water in rusty pipes has an unpleasant odor and becomes suitable only for technical use.

Corrosion in heating pipes reduces heating efficiency, which inevitably increases operating costs.

Methods for cleaning rusty pipes

The appearance of corrosion can occur both on the outside and on the inside of the pipe. Cleaning methods depend on the localization of plaque and the degree of damage.

It is not necessary to clean heavily corroded pipes from rust - this can damage them, and as a result, the pipe will become unusable. Therefore, in the case of severe corrosion damage, it is much more expedient to simply replace the damaged section of the pipeline or the entire line.

Only if the pipe is slightly damaged by rust, cleaning will be effective and increase the life of the pipe for some time.

Cleaning the pipe from the outside

If the pipe is rusted on the outside, you can use:

Note! Special rust removers should be used strictly following the instructions and dosage. They contain strong alkalis, which, if the instructions are violated, can damage the pipes.

Cleaning the pipe from the inside

In addition to corrosion, scale and various deposits accumulate on the inner walls of pipes. To maintain the throughput of the pipe, it is necessary to regularly clean and flush it from the inside for preventive purposes.

Painting heating pipes is a typical task that occurs where the system has not been replaced with options made of plastic, stainless steel, copper. How to tidy up a conventional system so that it looks its best? The reliability of protection is also important, the paint must be resistant to temperatures and external influences, not to bring harmful substances inside the house. Therefore, its selection and application must be approached carefully ...

Pipes are serious...

Painting and protection of heating pipes is best done according to the rules, otherwise there will be increased costs.

If you do not make high-quality protection of steel pipes from the very beginning, then under a layer of paint the metal will rust. This will be manifested by swelling, peeling of the layer, rust in places. Then it will be necessary to mechanically peel off the rust and the old paint, after which ... do it according to the rules - there will be triple labor costs and financial frustration.

The intensity of corrosion will depend on the environment, on humidity. Outside, steel parts that are exposed to precipitation oxidize intensely. In contact with the ground, this process is even faster.

In a room, especially in a dry and heated one, this process is slow. But surely many have seen rust on radiators and pipes, even painted ones. How to process these parts reliably, especially when it comes to operation in adverse conditions?

Painting of steel parts

Steel and cast iron are painted according to the following scheme.

• 1. Mechanical removal of rust, old paint, cleaning of dirt to metal, solvent degreasing.
• 2. Treatment of the entire surface and internal cavities with a rust inhibitor. Orthophosphoric acid is more commonly used. This is an important point. When the acid reacts with iron oxides, stable substances are formed in the form of a film on the part.
• 3. Metal primer. Soil - a special composition that is firmly associated with the surface of the part, enters into the smallest irregularities. Forms a strong protective film. It is recommended to use only high-quality compositions.
• 4. Painting. The paint layer must be resistant to external influences. Preferably from the same manufacturer as the primer for the best combination.

Additional information - the sequence of work when painting and protecting elements of the heating system is shown in the figure.

What is the feature of heating protection

Heating pipes and radiators get hot. At the same time, they are located in residential premises. Therefore, the compositions that can be used to paint the heating system should be:

• elastic, do not crack at constant temperature expansions. Do not lose adhesion to metal.
• do not emit any components, including when heated.

But not only that, for outdoor work, the compositions must also be resistant to freezing if the pipes hibernate without heating in the open. And also - to precipitation with aggressive acid-base water, and to ultraviolet radiation, if there is no external additional protection.

For outdoor use, the protection must be particularly resistant to electrochemical reactions, and for the ground - also to significant mechanical stress.

What is used for pipes

To the delight of the consumer, some modern paint products meet the above requirements. On sale you can find special compositions for heating heating systems.

As a rule, water-based surface paints are used for pipes and radiators inside the house. They are considered the most harmless and do not smell. But fillers can be different.

For outdoor use, oil-based formulations can be weatherproof. They dry longer, but the resistance of the film they created to the effects of aggressive waters is more important there. They can be applied to various pipes. True, the protection of heating mains outside buildings and in the ground is carried out in several other ways.

Heating main outside and underground

Heating pipes outside the building are usually thermally insulated. On them, in addition to the usual protection against corrosion, a sheath of insulation is installed. Thin pipes that are used in private homes are often wrapped in a shell made of dense polyurethane foam or extruded polystyrene. These thermal insulation materials are water-repellent, even if leakage occurs through the outer coating, they are likely to prevent further moisture from spreading.

The shell is put on the pipes in a checkerboard pattern, and the joints are glued with construction tape.

A roofing felt casing is glued over the thermal insulation using a composition that is not aggressive to polystyrenes, which acts as a long-term protection against moisture.

But larger diameters are thermally insulated more often with rolled glass wool. This way is cheaper. A bituminous-roofing material cover is arranged on top.

The pipes themselves under thermal insulation are usually treated with a rust inhibitor and a high-quality primer.

New silver pipe

One of the reliable methods of protecting heating pipes that can be applied at home is coating with a zinc-polymer composition. The so-called "cold galvanizing". This is not at all what is called factory galvanization, but nevertheless, protection is advertised as something else. Zinc dust is added to the polymer-epoxy composition, with a chip size of less than 10 microns. Suitable as a replacement for the usual "silver", as an option, although not cheap, but as an interesting experiment ....

What compositions are used - how to paint?

At present, the following series of paints are widely used for painting pipes

These and other coatings for heating pipes and radiators can be found on store shelves. True, they are only part of the necessary protection of the metal from corrosion. Full painting includes the processes that were listed above.

10790 0 5

Protection against corrosion of steel pipes: 3 gifts from the "old lady" of chemistry

Metal pipes have the highest strength characteristics, but they are also dominated by an incredibly destructive phenomenon called corrosion. Excessive moisture can destroy even the strongest steel. In this article, I will tell you about the methods I used to protect my own iron pipeline from such a detrimental effect, based on the knowledge of chemistry gained at school.

General provisions

Corrosion processes are the oxidation of a metal, in which its atoms change their free state, losing their electrons, to ionic. A pipeline laid underground is subject to two types of corrosion, the nature of which is worth understanding before starting to deal with them. Therefore, I will pay a little attention to their description:

Soil

As you may have guessed from the title and accompanying diagram, soil corrosion occurs when steel contacts the ground. In turn, it is divided into the following subspecies:

• Chemical. Appears as a result of exposure to iron gases and non-electrolytes of the liquid type. It is noteworthy that with it the material is destroyed evenly, and the formation of through holes is almost impossible, which makes this type of corrosion process the least dangerous for a pipeline laid underground;
• Electrochemical. The metal acts as an electrode, and groundwater, of which there are incredibly many in our climatic zone, is an electrolyte. The ongoing process is very similar to the work of a galvanic couple and provokes the destruction of point areas on the surface of pipes, which ultimately leads to their emergency state;

• Electrical. It arises as a result of the impact on steel of stray currents, which can “drain” from rails, substations and other electrified devices that fill modern cities. It is the most dangerous and destructive corrosion process.

Internal corrosion

If the transported liquid has a low pH, but the content of oxygen, sulfates and chlorides, on the contrary, is high, then internal corrosion processes cannot be avoided, as a result of which:

• The level of roughness increases the inner surface of the wall, which leads to a decrease in water permeability;

• The quality of the transported liquid is deteriorating, as rust gets into it;
• With time there may be a hole capable of causing a pipeline rupture.

Chemistry on guard

Corrosion protection of pipelines according to SNiP includes many different complex measures, but I want to give some specific methods that great science “gives” us so favorably, and which I managed to put into practice:

Gift #1: Outer Insulation

Above, we figured out that most of the troubles occur due to chemical reactions that occur as a result of long-term contact of the metal with the ground. Therefore, the simplest and surest step is to eliminate it completely. Moreover, in this case, it is also easy to protect pipes from freezing at the same time, that is, “we kill two birds with one stone.”

I will describe to you the option that I used myself, as well as alternative ways to isolate the pipeline being laid:

1. Petroleum bitumen. It was this material that I took as a basis for the implementation of metal protection against rust in underground operation. Its price fluctuates around 18-22 rubles per kg, which is quite favorable to the family budget. The working process:

• First of all, I'm up to shine cleaned the surface pipeline with a steel brush;

• Then I diluted part of the purchased bitumen with gasoline to obtain a bituminous primer in the following proportions:

• Thoroughly treated the metal surface with the resulting solution water main;

• Coming on fire prepared bituminous mastic with the addition of crushed asbestos to enhance the strength characteristics of future insulation. Cement and kaolin are also suitable for this purpose;

• He applied the first layer of hot mixture, after which he wrapped the pipeline with waterproofing. I used a model with these characteristics:

• Then he repeated the process two more times. For your region, you may need less or, conversely, more layers of bitumen with waterproofing, depending on the corrosive activity of the soil, which is influenced by its moisture level, chemical composition, acidity and structure;

1. Polyethylene. There are two completely different situations to note here:

• The first includes the hand-written execution of the plan. This method can be called the easiest to implement, since it will be enough for you to simply wrap the pipe in several layers with a plastic sheet and fix it with mounting tape. But by itself, this material has low strength characteristics, so I would be careful not to use it to protect long sections of the highway;
• In the second, we are talking about the factory application of reinforced extruded polyethylene. That is, you buy metal pipes with a special protective layer. Of course, such products will cost more, but they will give quite effective protection against corrosion;

1. polyurethane foam. Here you can also go two ways, but in any case, it is worth immediately noting the very high thermal insulation qualities of the finished anti-corrosion protection:

• Use special polyurethane foam shells. They are two halves of the cylinder, which are put on both sides of the pipeline and are joined to each other, creating a connection;

• Injection of liquid foam between the pipe body and a pre-installed sheath made of extruded polyethylene or other suitable insulating material. After solidification of the substance, the seams are completely absent, which, of course, significantly improves the quality of the insulation, although the process itself is more laborious in its implementation.

The above options for external insulation are not limited, here you can use many more moisture-resistant materials that can take a cylindrical shape. Therefore, in any case, also be guided by the current offers of a specialized store located near you.

Gift #2: Inner Insulation

As I noted above, the liquid transported through the pipes can also provoke the occurrence of corrosive processes, and here things are somewhat more complicated. The fact is that without special equipment at home, it is impossible to make high-quality internal insulation. It remains then only to order the appropriate services from specialists or immediately buy already protected products.

The most common option today is applying a cement-sand mixture to the inner walls of the pipeline followed by its crimping using a special dragged device. The result is a smooth, corrosion-resistant coating.

When I ordered this type of service, I was offered the following rates:

It is noteworthy that the instruction allows the processing of both new metal pipes and old ones.

In addition to cement, it can also be used petroleum bitumen. In this case, products with a large cross section are dipped into a liquid solution, and then the joints are processed manually. And samples with a small diameter are coated after welding, passing a mixture through them with a hollow copper cylinder under the influence of a direct electric current. Due to the action of electricity, bitumen particles adhere tightly to the iron, creating a thin, reliable film.

Gift #3: Active Insulation

This includes electrical protection methods that I was quite able to implement on my own. Here is their description:

1. cathodic protection:

• We impose a negative potential on the pipeline, transferring it to the cathode zone;
• Next to the pipes burying iron pipes, pieces of rail or other ferrous metal products that will take on the role of the anode;

• We connect a source with a negative direct current to the pipeline;
• We connect a source with a positive direct current to a rail or other product that you used as an anode;
• So a closed circuit of electric current is formed, which flows from the positive pole to the anode ground, spreads over the ground, hits the pipe and then to the negative pole;

• Since from the rails the current comes out in the form of positive metal ions, then it is she who is gradually destroyed, and not the pipe. That's chemistry for you;

1. Protective protection. Much easier to implement because does not require an external power supply. This is the one I prefer to use:

• We place a metal rod next to the water supply, having a negative chemical potential, which exceeds that of steel. It can be a product made of zinc, magnesium or aluminum;
• We connect it to the protected structure using ;

• The entire impact will fall on the anode protector, excluding pipe corrosion;
• After the zinc or magnesium rod is completely destroyed, it must be replaced;

1. Drainage. With it, pipelines are protected from stray currents:

• We connect the pipe with a cable to the nearest electrified source, through which the currents that have fallen on it return back;
• Metal ions cease to go into the soil, due to which corrosion processes stop.

Thus, all active protection methods are reduced to preventing the loss of metal ions due to the “sacrifice” or getting rid of stray currents.

I recommend using an integrated approach to waterproofing your pipeline. That is, to combine external, internal and active protection.
This will give the most effective result, allowing to extend the operational life of the line for decades.

Conclusion

When installing a water supply system in my own suburban area, I ordered processing of its internal walls with a cement-sand mixture, then independently outside covered it with bituminous insulation and for more confidence buried nearby a magnesium blank connected by a cable. Now I have no reason to doubt the durability of the created structure, since the existing knowledge of chemistry guarantees the absence of corrosive processes, taking into account all the precautions taken.

The video in this article contains some additional information that is directly related to the topic presented.

If you have any questions after reading the material, you can ask them in the comments.

If you want to express gratitude, add a clarification or objection, ask the author something - add a comment or say thanks!

Without reliable anti-corrosion protection, not a single metal structure will last for a long time. Rust protection is important unless you plan on replacing your fence every few years.

Metal fences are no exception. You can extend the life of products by properly processing them. Below we will talk about the technology of painting structures made of metal picket fence, profiled sheet and mesh, as well as analyze the coloring compositions that are best suited for metal surfaces.

Rust protection for the fence in stages

We start by preparing the metal for painting

This moment is fundamental, since it determines how well the finishing layer will lie on the fences from the eurostudent or profiled sheet. First you need to clean the fence from traces of paint, rust, oil, grease, dirt. Conservative and radical methods are appropriate here.

• Conservative ones include cleaning rust with a scraper, a metal brush, a special knife. The best result will give an acetylene torch or a blowtorch.
• When exposed to metal, the outer layer of paint burns out, and rust and scale move away due to temperature differences. If it is not possible to remove traces of corrosion, choose a coloring composition that is suitable for application to an unprepared surface.

Padding

The next stage is the application of a primer, which simultaneously protects the metal from corrosion and ensures that the paint adheres to the surface. For ferrous metals, experts recommend choosing anti-corrosion primers.

For non-ferrous, on the contrary, the property of adhesion is more important (aluminum and copper are not subject to corrosion). The primer coat can be applied with a roller, brush or sprayer.

Applying the finish coat

After the primer layer is applied, you can start painting. It can be applied with a sprayer, brush or roller.

It is better to paint in 2-3 layers with drying intervals. This will give a more uniform surface without flaws. The sprayer is the easiest to use. To do this, you need to process the surface from a distance of 15-20 cm.

The exposure time between layers is reduced to 20 minutes. Rollers are used for flat surfaces. Before painting, it is recommended to dilute the mixture with a solvent in a ratio of 9 to 1. Hard-to-reach places and corners are treated with a brush. Then all the fences are rolled in 2-3 layers.

The choice of paint for metal

On the masterovit.ru website (the largest manufacturer of metal fences in the Russian Federation in 2015), there was a discussion recently about how to properly paint an inexpensive fence made of corrugated board and what paintwork materials are better to choose.

The company's specialists recommend water-dispersion and special acrylic paints for metal. The latter option is preferable, since it allows you to reliably protect the surface from corrosion and negative external factors (precipitation, UV radiation).

A good solution is the choice of anti-corrosion compounds that are allowed to be applied to traces of rust and paint residue. The compositions contain a solvent, so they remove the old layer and protect structures from destruction. There are also enamels with additives on the market: rust converters, anti-corrosion primers. They are applied to clean surfaces.

Pre-treatment of the base with a primer is not required, which reduces the process of painting the fence. For ferrous metals, water-based anti-corrosion compounds are optimal. The topcoat is highly resistant to ultraviolet radiation, rainfall, sudden changes in temperature.

Corrosion is the scourge of all metal structures, and leaking pipes are a nightmare for any homeowner. The appearance of rust is inevitable, like the change of seasons, it is caused by physical and chemical environmental factors. But it is possible to slow down the development of corrosion and reduce its destructive effect.

Metal and plastic: pros and cons

The common opinion of experts in the field of repair says that there is only one radical way to combat corrosion - replacing all pipes with plastic ones. But metal pipes do not give up so easily, because it is not always possible to make major repairs in the entire apartment. In addition, steel and cast iron pipes are much stronger and more reliable than plastic and metal-plastic ones. They are more resistant to high pressure and temperature (especially to their differences), have a low coefficient of thermal expansion (do not deform) and high thermal conductivity.

Plastic is theoretically very durable, but this has not yet been tested by time. The safety of this material in its long-term use has not been sufficiently studied, but it is already known that it is afraid of chlorinated water. So metal pipes still have a place in our homes, which means that the problem of their protection against corrosion is still relevant.

Around the aggression!

How to deal with rust at home? The most affordable way is to apply a product to the metal that forms a protective film on its surface: paint, varnish, enamel. Paint coatings have low vapor and gas permeability and high water-repellent properties. Thus, they do not allow moisture, oxygen and other aggressive substances to the metal surface, which cause corrosion. Paints are relatively inexpensive, easy to apply with a regular brush or spray. They retain their protective properties for several years. Their important quality is resistance to high temperatures, the main drawback is sensitivity to mechanical damage and temperature changes, due to which small cracks form on the surface, opening access to moisture and air to the metal. Therefore, staining should be carried out regularly.

Main quality!

The barrier in the form of paintwork materials does not stop corrosion completely, but only slows it down. Therefore, the quality of the coating comes to the fore - high strength of adhesion of the composition to the base (adhesion), uniformity of application, absence of porosity and air bubbles. And the quality of the coating is directly related to how the base is prepared. Old, peeling paint must be carefully removed. If the pipe is rusty, then you need to clean off the loose layers, and then use a special rust converter (150-200 rubles / kg). The basis of such funds is acid (usually orthophosphoric). It chemically interacts with rust and turns it into iron salts - a neutral substance that forms a uniform and durable additional protective film.

Next, an anti-corrosion primer should be applied, and only then - a paint compatible with the primer. The thicker the layer of the latter, the worse the adhesion to the base. Therefore, the main rule is that several thin layers of coating are better than one thick one.

The range of anti-corrosion coatings is quite extensive. The simplest ones are GF-021 primer (the cost of this product from Khimservice is 50 rubles / kg) and PF-115 enamel (for example, the price for this material from RegionSnab is 48 rubles / kg). More expensive, but also effective - polyurethane, alkyd, epoxy coatings, which not only protect the metal well, but also have excellent decorative properties (in particular, "liquid plastic" enamel). It is good if the paint contains corrosion inhibitors - substances that slow down oxidation. The most convenient to use products that are united by the name "3 in 1 rust paint" (about 200 rubles / kg) - they simultaneously contain a rust converter, anti-corrosion primer and wear-resistant enamel.

What's underground?

Pipes passing underground are especially susceptible to corrosion - they cannot be dispensed with in a suburban area. A different corrosion mechanism occurs in soil than in the atmosphere. The main cause of soil corrosion is electrochemical factors: a metal pipe in the soil becomes an electrode, and wet earth becomes an electrolyte.

To isolate the pipeline from this aggressive environment, paintwork materials are unsuitable, since the protective layer is mechanically damaged when it comes into contact with the ground. Much more practical are elastic coatings based on coal tar (bitumen) with various additives, mineral or polymer, that increase its strength. Such a mixture is called bituminous mastic (from 25 rubles / kg). Another option is to wrap the pipes with any insulating material, for example, waterproofing (from 40 rubles / sq. M), which is asbestos paper coated with bitumen with the addition of cellulose.

What's new?

A relatively new effective and inexpensive method of protection against soil corrosion is the use of geotextiles (from 20 rubles/sq. m.). This non-woven polymer fabric has excellent water and air permeability, is durable, wear-resistant and withstands high mechanical loads and aggressive environments. Geotextile creates a reliable separating layer between the pipe and the soil. The best effect will give the simultaneous wrapping of the pipe, lining the trench and good drainage. At the same time, water entering the soil does not linger, which means that it does not have time to act on the protective coating of the pipe. Synthetics practically do not decompose in the soil, which allows drainage based on it to function for a long time. Working with geotextiles is simple and does not require special skills.

A truly unique method of protection is cold galvanizing. Metal-polymer compositions (200-350 rubles / kg) have a protective effect, which is comparable to galvanizing performed in the traditional way - hot or galvanic. Such compositions provide protection in water, soil, atmosphere for many years, they are used both for obtaining independent protective coatings and as primers before applying coatings. The cold galvanizing system contains a binder - polystyrene, epoxy, alkyd and other bases and zinc powder ("zinc dust"), in which about 95% of metallic zinc with a particle size of less than 10 microns. The composition is applied like ordinary paint - with a brush or roller. After drying, a polymer-zinc film is formed on the surface, which combines all the advantages of polymer and zinc coatings: the first forms a mechanical barrier protection, and the second - an electrochemical one. In addition, such a coating is sufficiently elastic and does not give microcracks, and it is also easy to repair.

Proper anti-corrosion protection will help preserve the original appearance of various metal structures and pipes. Subject to the choice of quality materials, proper application, careful preparation of the surface, it will save you unnecessary costs, save time and effort.