How to protect fence pipes from corrosion inside. How to protect pipes from corrosion. Chemical treatment of aggressive water

Almost any system internal infrastructure and life support residential buildings, municipal and commercial buildings or industrial facilities, by and large, is a developed network of pipelines connecting various objects of the system to each other in a certain order.

In most cases, for example, when arranging a gas pipeline, hot and cold water supply, fecal or cable and ventilation, underground, air or internal laying of metal pipes of various diameters and sizes is used.

Depending on the operating mode and conditions environment, metal pipes during operation can be subjected to prolonged exposure to various adverse factors. To solve this problem, a comprehensive protection of pipelines against corrosion was specially developed according to SNiP 2.03.11-85 "Protection building structures from corrosion."

Corrosion Control Methods

To help the reader understand how to maximize the durability of the pipeline, this article will consider some options for active and passive protection of metal products that are part of pipeline utilities.

Also there will be detailed instructions, which describes in detail the basic principles for the implementation of anti-corrosion protection for metal products intended for operation in aggressive conditions.

Classification of harmful factors

As mentioned above, the nature and degree of influence of external factors largely depends on specific conditions operation, such as the location of the pipe, the chemical composition of the soil, the average annual temperature and relative humidity environment, presence of direct current sources nearby, etc.

According to the mechanism of occurrence and the degree of destructive impact, all harmful factors can be conditionally divided into several types.

1. atmospheric corrosion occurs when iron interacts with water vapor, which is contained in the surrounding air, as well as as a result of direct contact with water during precipitation precipitation. During the course of a chemical reaction, iron oxide is formed, or, more simply, ordinary rust, which significantly reduces the strength of metal products, and over time can lead to their complete destruction.

1. Chemical corrosion occurs as a result of the interaction of iron with various active chemical compounds(acids, alkalis, etc.). At the same time, the flowing chemical reactions lead to the formation of other compounds (salts, oxides, etc.), which, like rust, gradually destroy the metal.
2. Electrochemical corrosion occurs when the iron product is in the electrolyte environment for a long time (an aqueous solution of salts of various concentrations). In this case, anode and cathode sections are formed on the metal surface, between which an electric current flows. As a result of electrochemical emission, iron particles are transferred from one area to another, which leads to the destruction of a metal product.
3. Impact of negative temperatures in cases where pipes are used to transport water, it leads to its freezing. Upon transition to a solid state of aggregation, it forms in water crystal cell, as a result of which its volume increases by 9%. Being in a closed space, water begins to put pressure on the walls of the pipe, which ultimately leads to their rupture.

Note! A significant difference in average annual and average daily temperatures leads to significant fluctuations in the total length of the pipeline, which are caused by linear thermal expansion of the material. To prevent rupture of pipes and damage load-bearing structures, after a certain distance on the line it is necessary to install thermal compensators.

Soil analysis

In order to choose the most effective method of protection, it is necessary to have accurate information about the nature of the environment and the specific operating conditions of the steel pipeline. In the case of laying internal or overhead line this information can be obtained on the basis of subjective observations, as well as on the basis of the average annual climatic regime for a given region.

In case of laying underground pipeline, corrosion resistance and durability of the metal largely depend on the physical parameters and chemical composition soil, therefore, before digging a trench with your own hands, it is necessary to submit soil samples for analysis to a specialized laboratory.

The most important indicators that need to be clarified in the analysis process are the following soil qualities:

1. The chemical composition and concentration of salts of various metals in groundwater. The density of the electrolyte and the electrical permeability of the soil largely depend on this indicator.
2. Qualitative and quantitative indicators of soil acidity, which can cause both chemical oxidation and electrochemical corrosion of the metal.
3. Soil electrical resistance. The lower the value electrical resistance, the more the metal is exposed to the damaging effects caused by electrochemical emission.

Advice! To obtain objective results of the analysis, soil samples must be taken from those soil layers in which the pipeline will pass.

Low temperature protection

In the case of underground or air, the most important condition for their uninterrupted operation is the protection of pipes from freezing and maintaining the water temperature at a level not lower than 0 ° C during the cold season.

To reduce the negative impact of the environmental temperature factor, the following technical solutions are used:

1. Laying an underground pipeline at a depth exceeding the maximum freezing depth of the soil for a given region.
2. Thermal insulation of air and underground lines with help various materials with low thermal conductivity ( mineral wool, foam segments, foam sleeves).

1. Backfilling the pipeline trench bulk material with low thermal conductivity (expanded clay, coal slag).
2. Drainage of adjacent soil layers in order to reduce its thermal conductivity.
3. pad underground utilities in rigid closed boxes made of reinforced concrete, which provide the presence air gap between pipe and soil.

Most progressive method How to protect pipes from freezing is to use a special casing, consisting of a shell made of heat-insulating material, inside which an electric heating element is laid.

Note! The depth of soil freezing for each specific region, as well as the method of its calculation is regulated normative documents SNiP 2.02.01-83* "Foundations of buildings and structures" and SNiP 23-01-99* "Construction climatology".

External waterproofing coating

The most common way to combat metal corrosion is to apply a thin layer of durable waterproof protective material to its surface. The simplest example of an external protective coating is a conventional waterproof paint or enamel, for example the protection of a gas pipe passing through the air, is always done with yellow weather-resistant enamel.

Underground water and gas pipelines are usually assembled from pipes that are pre-coated on the outside with a thick layer of bituminous mastic, and then wrapped with thick technical paper. Also high efficiency have coatings of composite or polymeric materials.

Metal elements of sewer underground communications from the inside and outside are covered with a thick layer cement-sand mortar, which after hardening forms a homogeneous monolithic surface.

To choose on your own suitable material for outdoor coating, you need to know that for maximum protection it must have several qualities at the same time.

1. The paint coating after drying should have a continuous, uniform surface with high mechanical strength and absolute resistance to water.
2. Protective film waterproofing material, with the specified properties, must be elastic and not collapse under the influence of high or low temperatures.
3. The starting material for coating should have good flowability, high hiding power, as well as good adhesion to the metal surface.
4. Another indicator of a quality insulating material is that it must be an absolute dielectric. This property provides reliable protection pipelines from stray currents, which increase the adverse effects of electrochemical corrosion.

Advice! Most effective solutions to isolate metal from the environment, it is customary to consider compositions based on bituminous resins, two-component polymer compositions, as well as rolled polymer materials self-adhesive.

Active and passive electrochemical protection

Underground engineering Communication more prone to corrosion than air and internal pipelines, because they are constantly in the electrolyte environment, which is a solution of salts contained in groundwater.

In order to minimize the damaging effect caused by the reaction of iron with a water-salt electrolyte solution, active and passive methods of electrochemical protection are used.

1. Active cathodic method consists in the directed movement of electrons in a constant circuit electric current. To carry it out, a pipeline is connected to the negative pole of the DC source, and an anode ground rod is connected to the positive pole, which is buried in the ground nearby. After applying voltage electrical circuit closes through the soil electrolyte, as a result of which free electrons begin to move from the ground rod to the pipeline. Thus, the ground electrode is gradually destroyed, and the released electrons, instead of the pipeline, react with the electrolyte.

1. Passive sacrificial protection of pipelines It consists in placing an electrode made of a more electronegative metal, such as zinc or magnesium, next to iron in the ground and electrically connecting them together through a controlled load. In the electrolyte environment, they form a galvanic couple, which during the reaction, as in the previous case, causes the movement of electrons from the zinc protector to the protected pipeline.
2. Electrical drainage protection is also a passive method, which is performed by connecting the pipeline to a ground loop, made in accordance with the PUE. This method helps to get rid of the occurrence of stray currents and is used if the pipeline is located near the contact electrical network of ground or rail transport.

Note! good example passive protective protection is the well-known zinc coating of iron products, or, more simply, galvanization.

Conclusion

Each of the above methods has its own advantages and disadvantages, so they should be used depending on the prevailing specific conditions. In conclusion, it should only be said that, regardless of the method chosen, the cost of repairing and replacing a pipeline will be much more expensive than the cost of the most complex and time-consuming protection.

For more information, you can watch the video in this article or read similar materials on our website.

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 conventional system so that she has best view? 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 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 rust, old paint, cleaning of contaminants to metal, degreasing with a solvent.
• 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 for coloring heating system, must 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 open form. 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 formulations for hot heating systems.

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

For outdoor work, weatherproof compositions can be oil based. 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, which are used in private homes, are often put in a shell made of dense polyurethane foam or extruded polystyrene. These thermal insulation materials water-repellent, even if leakage occurs through the outer coating, they are likely to prevent further penetration of moisture.

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

On top of the thermal insulation, a roofing material casing is glued using a composition that is not aggressive to polystyrenes, which acts as a long-term protection against moisture.

But large 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. Indeed, they are only part of necessary protection metal from corrosion. Full painting includes the processes that were listed above.

Corrosion is one of the main problems of all metal structures. Many experts believe that the appearance of rust is an inevitable process, and their only recommendation is to change metal pipes to plastic ones. However, given the fragility of plastic, such perturbations can not be carried out everywhere. In addition, the development of corrosion can be slowed down by significantly reducing its destructive effect.

There are several ways to combat corrosion of profile pipes in Moscow, and the easiest of them is to apply to metal special means forming a protective film on its surface. Such a tool can be paint, varnish or enamel. Paint and varnish coatings are characterized by low gas permeability and gas permeability, as well as the ability to water repellency. Such coatings do not allow the metal to come into contact with moisture, oxygen and other aggressive substances that cause corrosion. Coatings are relatively inexpensive and very easy to apply. For this, an ordinary brush is used. A spray option is also available.

Protective qualities paintwork materials persist for several years, after which the layer must be updated. They have several disadvantages:

1. Do not withstand significant mechanical damage.
2. Not resistant to temperature changes.

As a result, over time, cracks form on the surface of painted pipes, so this type of protection should be carried out regularly.

How to properly prepare a pipe for painting

In order to reliably protect the pipe from corrosion, it is necessary not only to use high-quality protective substances, but also to take care of their correct application. First of all, it is necessary to achieve high adhesion, that is, the quality of adhesion of the applied composition to the metal. This method of combating corrosion on profile pipes in Moscow assumes a uniform layer of application, the absence of air bubbles and porosity. Therefore, the quality of the coating will directly depend on the preparation of the base.

Corrosion is the scourge of all metal structures, and leaking pipes nightmare 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 overhaul throughout the apartment. In addition, steel and cast iron pipes much stronger and more reliable than plastic and metal-plastic. 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 during 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 in living conditions? Most affordable way- application to the metal of a product 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 save protective properties for several years. Their important quality is resistance to high temperatures, the main disadvantage is sensitivity to mechanical damage and temperature changes, due to which small cracks, 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, enamel "liquid plastic"). 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 - in a suburban area you can’t do without them. A different corrosion mechanism occurs in soil than in the atmosphere. The main cause of soil corrosion is electrochemical factors: 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 protective layer mechanically damaged when in 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, hydroisol (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. Best effect will give simultaneous pipe wrapping, trench lining 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 made traditional way- hot or galvanized. Such compositions provide for many years protection in water, soil, atmosphere, they are used both to obtain 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. Apply composition as regular paint- brush or roller. After drying, a polymer-zinc film is formed on the surface, combining 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 corrosion protection will help maintain original view various designs and pipes made of metal. Subject to choice quality materials, correct application, careful surface preparation it will save you from extra costs saves time and energy.

There are many options for building fences, and their differences depend on the functions for which they are intended. In accordance with the functions, the material of the future fence is selected.

Functions and material of the fence

The fence is intended for simple and specialized fencing of the territory: land plots that are in private ownership, parking lots, recreation areas, construction and specially protected objects, animal pens. Also, fences are often an element of decor in landscape design or form a single composition with architectural solutions.

This variety of functionality makes it possible to use different materials for their construction: ordinary wooden or metal fence, decorative fence in the Ranch style, multi-colored profiled sheets, chain-link mesh, welded, sectional, forged, asbestos-cement and concrete spans. Like any structure, the fence involves the creation of some kind of foundation on which the material is attached. For the fence, the pillars are such a basis.

Pole material

Regardless of the choice of material for the fence itself, the poles can be made from:

• tree;
• metal;
• concrete;
• bricks;
• asbestos cement pipes.

Metal advantage

Universal material for the manufacture of fence posts are metal products, because in the vast majority of cases of fence installation, welding is used.

special quality metal poles is their durability. No matter how you process wooden beam, it will rot much faster than the metal will collapse.

The process of metal corrosion occurs on average at 0.15 - 0.2 mm per year. It depends on the external weather and climatic conditions, the composition of the metal and the quality of its processing. positive plus metal poles is reliability and durability. Asbestos-concrete pipes are not subject to corrosion and do not require additional care, but they are fragile and cannot withstand rough mechanical loads.

Pillars made of metal, compared to reinforced concrete, are easily repaired and installed, dismantled and can be reused.

Corrosion

Metal corrosion is a natural phenomenon, which cannot be completely prevented, but this destructive process can be significantly slowed down. The oxidation process takes place with the participation of oxygen and aqueous solutions containing acid, alkali or salt.

In nature, iron is not found in its pure form, but is found in iron ore. Mankind invented the production of steel and came up with ways to preserve it. The factories use methods of phosphating steel by immersing it in various solutions, as well as electrochemical treatment. Such a coating is in the nature of a primer and requires subsequent painting. Steel is coated with other metals. Of the cheaper ones - aluminum and zinc.

There are silicate coatings - this is different kind enamel. The enamel is fragile and not quite suitable for a fence. Cement has approximately the same expansion temperature as steel and serves as an insulator against aggressive environments. A good insulation is a polymer film applied in several layers at the factory.

Treatment

The durability of the metal depends on the grade of steel. More precisely, there is alloy steel with different additives. But for a simple fence - this is an expensive pleasure. Usually they use factory rolled metal, or make poles with their own hands from what you can get. For temporary fences, poles welded from pieces of iron or previously used, but still strong pipes from water supply, are suitable.

It is difficult to clean the inner cavity of the pipe, and rust is removed from the outside with an iron brush, treated with a grinder or grinder. If necessary, degrease and apply a primer for metal, for example, GF-021. After the primer dries, the pipe is painted in two layers.

To paint metal, the most common oil paint PF-115 is suitable. For the lazy, there is a three-in-one paint. It neutralizes rust, primes and creates a protective surface.

But in practice, without prior machining it is better not to do without, you must at least clean the metal with sandpaper.

The best solution for choosing new fence posts would be combined option metal coated with zinc and polymer film. Factory rolled metal produces painting, observing all technologies. It is best to purchase poles ready for installation, as this will significantly save time and labor costs. However, this option cannot be called financially economical.

In practice, most often iron poles self-priming and painting with oil paint or bituminous varnish

There are special spray paint cans that are convenient to use during welding. Powder coating will be more expensive and technically more difficult. The thinner the cover layer, the more durable the protection. Therefore, make several layers with a spray or carefully rub with a brush, avoiding air bubbles that provoke an oxide reaction.

The ground is over aggressive environment than air. Therefore, the part of the metal in the ground is insulated with concrete or bituminous mastic. Roll insulators are not suitable for these purposes. Scale, which occurs during welding, stimulates the corrosion of the metal. It must be removed with a grinder.

Forms of metal poles

Fence poles can have a wide variety of configurations, from simple to designer:

• round;
• square;
• rectangular;
• screw;
• homemade.

Round pipes the easiest and cheapest to buy. The choice of their diameter depends on the design of the fence, and most often they use a size from 57 mm to 108 mm, in exclusive options the diameter is increased to 159 mm. The thickness is selected taking into account the characteristics of the material being filled in the spans: from 1.5 mm to 4 mm. The thicker the longer term operation.

A good option with drill pipes, the wall thickness of which is 5 mm.

The transverse logs are attached directly to the pipes by welding, or guides for fasteners are welded onto the pipes. Guides can be made in advance by welding them to a clamp, which is put on the pipe and tightened with a bolt. With this installation option, an insulating pad made of cotton material or a special plastic lining suitable for the pipe diameter is placed under the clamp.

Profiled columns have the shape of a square or rectangle. This form makes it possible to fasten the log not only by welding, but also with the use of bolts or rivets. It is more convenient to work with them if the guide lags are made of wood or the fence is built in the Ranch style.

Screw posts are a pipe with a drill welded on its end. This option is used for quick installation fence, because there is no need to pre-dig a hole for the post.

Homemade poles they are made from used material that is available (orphan), or from one that can be obtained. Suitable, for example, iron corners.

Ground influence and installation

The choice of metal poles also depends on the method of installation, and it, in turn, depends on the condition of the soil. For an easy fence, it is enough just to drive a post into the ground if it is dense (serozem, clay, sand). Two people are involved in the work - one drives in, and the other holds the pole, checking it according to the level in two vertical planes.