Internal protective coatings of pipelines. Methods of anti-corrosion protection of pipelines and requirements for them

Corrosion is a specific process in which solids break down over time. This can happen not only due to certain chemical reactions. Sometimes corrosion is the result of electrochemical processes. It often appears on the surface of a substance and indicates that its subsequent destruction has begun. Some chemical elements are capable of reacting with the environment, as a result, corrosion can form on some surfaces, destroying even durable materials.

There is corrosion that shows up on various materials. However, the most common is the corrosion of metals. Because of this result of a chemical reaction, the economy of many countries suffers serious losses. The thing is that the most common type of corrosion is rust, because of which sometimes it is necessary to change the entire metal structure.

At the moment, pipes with an anti-corrosion coating are becoming increasingly popular, allowing them to maintain the overall performance of the device of which they are a part. Thanks to this development, most manufacturers of various products breathed a sigh of relief. After all, now there is no need to dismantle and re-install pipes that have been damaged by metal corrosion in a few years.

There are two main types of corrosion, differing in the degree of damage that it can cause. Distinguish between direct and indirect corrosion.

If corrosion has caused direct damage, in this case the metal coating cannot be restored. Therefore, you will have to change all the equipment, which consists of metal parts. If corrosion has already damaged the metal, it is best to provide anti-corrosion protection. It, in turn, costs a lot of money, however, after treatment with special substances and chemical solutions, the updated metal coating will no longer be subjected to oxidation and destruction from corrosion.

For this reason, it costs a lot of money. However, after treatment with special substances and chemical solutions, the renewed metal coating will no longer be subject to oxidation and destruction from corrosion.

If the damage was indirect, only some parts of the metal structure are replaced.

In this case, funds will go to:

• purchase of the corresponding metal,
• reducing the power of the equipment, if the metal structure consists of pipes and other similar equipment,
• improvement of products, the main element of which is a metal frame.

Corrosion protection is the main task of modern designers who develop various metal parts. In order for the structure to serve for several decades, it is necessary to create all the conditions for its protection from the influence of external factors and various atmospheric phenomena, the ability to influence the structure of the metal.

Modern technologies make it possible to develop an anti-corrosion coating of steel pipes, which provides a metal structure with additional protection against chemical elements that often come into contact with its surface.

Since at the moment oil and gas are becoming increasingly popular as universal fuels, it is worth considering how to ensure high-quality transportation for them.

Therefore, it is important to create such pipes at enterprises that would be protected by a special anti-corrosion coating that prevents the destruction of the walls of the pipes or the occurrence of corrosion on their surface, which leads to their destruction.

Projects are being created that would be designed to improve energy security in a particular country. We can say that in our time in the world there is an industry boom in pipeline transport. Thus, a situation was created that allowed for the construction of pipeline systems that could become an alternative to the existing ones.

Russia is a rapidly developing country, which is trying to invent and develop new and perfect types of protective coatings. Surprisingly, our specialists have already created pipes containing polyethylene insulation.

It is important to be aware of the fact that only a professional who understands such issues can qualitatively install such pipes.

It is no secret that technologies that provide solutions to such problems were invented several decades ago. If the pipe has a 3-layer polymer insulation, consisting of several layers, then the insulation of the joints of the pipes should be similar. The only type of this type of insulation will be heat-shrinkable cuffs.

In order for the metal structure to last longer, it is necessary to treat the coating with special substances to prevent the formation of corrosion on the surface of the material.

The most common pipes with an internal anti-corrosion coating, because thanks to the protective layer, they last longer. Special chemicals that will subsequently protect metal pipes are applied to their inside. At the same time, if corrosion provokes rust on the outer surface of the pipe, it will be more difficult to prevent its spread. In this case, manufacturers try to worry in advance about the safety of the entire surface of the pipe.

Therefore, the cost of such equipment, consisting of several metal parts, will be much higher. Manufacturers indicate on the accompanying instructions for the product, the application of special protective substances to the metal.

If there is no such protection, the pipe can last for several years until the external factors affecting its surface lead to partial or complete destruction of the metal.

At the same time, it does not matter where the pipe is located indoors or outdoors. Even if it is part of communications and is located in sea water, its surface is affected by various chemicals.

Particularly in need of corrosion protection are:

• various types of pipelines located not only in the open air, but also in water,
• equipment, the main part of which is metal,
• metal frames of various residential premises and buildings of industrial type,
• all kinds of tanks
• construction cranes,
• bridges,
• heat exchangers.

There are also pipes with an external anti-corrosion coating, designed specifically for subsequent installation in enterprises and industrial workshops, where most of the main chemical reactions and processes that speed up the production of goods often take place.

The external protection of pipes against corrosion is as important as the internal one. However, if the manufacturer does not have additional financial resources for the purchase of appropriate equipment, significant financial savings can be made if this type of pipe is purchased. Russia is currently investing heavily in the development and subsequent production of special substances that protect pipes from rust and other signs of corrosion on their surface.

Some regions of Russia have a humid climate. This is an ideal place for the appearance of not only rust on the walls of metal coatings, but also as a result of corrosion, which completely destroys metal coatings of any thickness and shape. Considering all the above factors, corrosion is currently the main problem that does not allow our country to develop fully. When our specialists are able to establish the production of special substances designed for anti-corrosion protection of metal surfaces, the state will save significant financial resources that are spent annually on the purchase of such chemical compounds abroad.

In addition, there is no need to change pipes and other metal coatings after a while, the service life of which expires due to rust and corrosion that destroys their surface.

The use of anti-corrosion protection means can significantly reduce material losses in most developed countries of the world.

At the same time, Russia needs to take its place among the producers of such goods. This will allow our country to take a leading position not only in the production of necessary goods and chemical elements that prevent the destruction of metal surfaces. In this way, it will be possible to conclude a sense of mutually beneficial contracts that will allow Russia to cooperate with other states.

There are several ways to apply an anti-corrosion protective coating to a metal surface. The most common is the barrier method of metal surface treatment. That is, the application of the substance occurs directly on the coating surface itself. Even if at the same time it contains additional chemicals, anti-corrosion protection will fulfill all the functional characteristics and properties assigned to it. For example, if a metal surface is painted with some paintwork materials or contains impurities of other substances and materials such as nylon, the substance will not enter into various chemical reactions with them, but will retain a strong structure.

Just as paints and varnishes create a protective film on the surface of the material, anti-corrosion agents form an additional coating, which in turn is not washed off with water. Over time, even such anti-corrosion substances lose their properties. Therefore, over time, it is necessary to repeat the processing procedure.

However, before choosing certain means for protecting a metal surface, it is also necessary to take into account the characteristics of the metal itself. Even the conditions under which the process of applying the substance to the metal plays an important role for its further operation and performance.

Therefore, Russian manufacturers seriously thought about creating an effective inexpensive tool for protecting metal surfaces from damage and all kinds of corrosion effects.

Technologists have already achieved certain results by developing several universal compositions that interact with most metals. But they still need to be refined and further improved. Subsequently, these compounds and substances will provide full protection for pipes and other metal structures.

Anti-corrosion coating of steel pipes

Table. Main characteristics of coatings and materials used to protect steel pipelines.

Depending on the requirements of the State Standard and the circumstances of the modern market, the necessary types of materials and technologies are used to ensure the anti-corrosion protection of pipelines.

As a hand tool for degreasing small local areas, rags and brushes are used, as well as solutions containing alcohol, acetone and other solvents. In industrial conditions, it is advisable to use automated mechanisms that supply a concentrated alkaline solution to a steel surface under pressure. This method is used to clean large fat deposits. After processing and waiting for the action of the composition on the contaminated area, the pipeline is washed with clean running water until soap and alkali residues are completely eliminated. After the procedure, the metal surface must be dried and inspected for lint or unwashed areas. The degree of degreasing must correspond to the 1st degree of degreasing in accordance with GOST 9.402-2004.

Blast cleaning produces a roughness of 50-110 microns on a steel surface, depending on the surface preparation requirements for a specific anti-corrosion insulating material.

After completion of abrasive blasting, dedusting is carried out. Dedusting of the surface of the pipeline is carried out by blowing compressed or using.

The quality of compressed air is subject to the requirements of GOST 9.010-80. The air from the nozzle must be free of moisture, oils and other compounds, so as not to spoil the steel or already painted surface. The use of acid or other inhibitors after abrasive blasting is not permitted.

The quality control of the steel surface preparation parameters is carried out using measuring instruments and visually:

• the degree of cleaning is controlled visually by photographic standards in accordance with ISO 8501-1;
• the degree of dust removal by testing the presence of dust with adhesive tape according to ISO 8502-3;
• roughness is measured with an electronic profilometer or comparator by comparison with a standard according to ISO 8503-1;

If cleaning using automatic mechanisms is not possible (hard-to-reach places, heights, etc.), manual work must be done. For this, brushes with wire bristles or mechanical devices are used. Care must be taken in their use. It is impossible to prevent the formation of defects that require re-treatment of pipelines - burrs, scratches, excessive roughness. Polishing of areas is also prohibited, which in the future can negatively affect the adhesion of the metal to paintwork materials. Surface treatment must necessarily go with the overlap of adjacent sections by at least 25 mm, if any. According to ISO 8501-1, the degree of cleaning of the steel surface should be Sa3.

If non-paintable surfaces are present, they must be protected with masking tape, sealing the nodes at a distance of at least 10 mm from the edges. The maximum indent is 100 mm.

2. .

The first (ground) layer is applied to the steel surface of the pipelines only after all cleaning processes have been completed. It is strictly not allowed to use coatings on metal, where there are pockets of rust, chalking or any other type of pollution. The surface must be absolutely dry before applying the paint.

High-build two-component coatings with a dry film thickness of 1 to 3 mm are applied using special high-performance airless sprayers for high-viscosity paints and varnishes with separate supply and heating.

Thin-layer two-component and one-component coatings can be applied with less productive installations for medium and low viscosity materials with separate or inseparable supply of paints and varnishes.

Paints and varnishes before application undergo additional input control, after which they are prepared for work in accordance with the technical documentation.

Coatings are applied on a clean and dry surface, preferably at an ambient temperature of +5°C and a humidity of not more than 80%. The temperature of the metal during application must be at least 3°C ​​above the dew point.

Control climatic parameters: air temperature, air temperature, air humidity, dew point temperature and the difference between the substrate temperature and the dew point; are carried out during the entire coating process using multifunctional measuring instruments such as Elcometer 319.

The final dry film thickness must comply with the specification and requirements for coatings.

Each subsequent coat of paint must be applied to the previous one when it is completely dry. Compliance with time intervals is important, as negligence will affect the quality of the overall work. If the previous layer has been in contact with the atmosphere for at least 30 days, then it is quite possible that deposits of salts, grease, moisture and dirt form on the surface. They are immediately eliminated by flushing the pipeline with clean water at a pressure of at least 250–300 bar. Some of the defects cannot be washed, so it is necessary to take a number of measures to restore the integrity of the layers. This is cleaning from scale or rust, smoothing ridges and swellings, grinding and roughening.

Control over the quality of work to protect pipelines from corrosion is carried out by quality inspectors. They use special instruments and also conduct the surface of the object.

Visual inspection consists in identifying defects in the painted surface of the pipeline. Each layer is controlled by the requirements of ISO 19840. The standard determines the thickness of the film, after its final curing. If places are difficult to access (structural units, zones), special devices are used for them.

Visual inspection is necessary to establish the presence of visible defects in the coating. Special measuring instruments examine:

• Degree of bond between surface and coating. For this purpose, an adhesive meter is used.
• The flaw detector shows the quality of the coating at the expense of continuity.
• The thickness gauge determines the dry film thickness of the coating.

The quality of the work performed is reflected in the documents during the delivery and acceptance of the object. In addition, this document is accompanied by:

The guarantee of the quality of work differs from the service life of protective compounds and is prescribed as a separate clause in the contract with the participation of two parties - the Contractor and the Customer. The specific service life of paint and varnish systems (up to 15 years) should provide reliable protection for metal structures (in particular, pipelines) from corrosion and fire. The position is spelled out in ISO 12944-5.

To get more detailed information, you need to contact the e-mail address or phones of the company "VekFort".

The main reason that has a significant impact on the life of pipeline systems is corrosion. Today, there are a huge number of methods to prevent corrosive wear, but the most popular of them are those that have a lower cost. Of course, no one claims that products should be used in construction and only stainless steel equipment, in some cases it is not justified expensive and unprofitable. And polyethylene pipes, which are highly resistant to corrosion and therefore so popular today, are not able to withstand high pressure, and therefore their use is limited.

For a long time, steel pipes are still widely used in construction, which, when laid in the ground without an anti-corrosion coating, quickly wear out and become unusable. Due to low efficiency and short service life, the use of bitumen and roll materials based on it is reduced. In their place come more modern materials, such as bitumen-polymer mastics, which are ready to use right out of the package and can be used to treat any surface.

There are situations when anti-corrosion treatment of the pipeline is required at the factory using specialized equipment. Quality control carried out for each individual operation during coating, allows you to achieve an excellent result. Currently, there are several methods to improve corrosion resistance, for example:

— three-layer isolation on the basis of polyethylene. Pipes are first treated with a primer coat consisting of adhesive and epoxy layers, which form a hard surface with excellent adhesion. Then polyethylene is applied to this surface, which prevents the formation of corrosion.

- silicate enamel. This coating is one of the most expensive, so it is used in the construction of critical pipeline systems in the nuclear, oil and gas industries. The advantage of this treatment is not only reliable protection against corrosion - the walls of the pipes become so smooth that suspended particles do not accumulate on their inner surface.

- foam polymer-mineral (PPM) insulation is a foamed polymer mass into which a mineral filler is introduced, such as ash or clean sand. Such foam, in addition to the anti-corrosion coating, effectively protects pipes from heat loss, so it is often used in the construction of heating networks.

All metal pipe products used in construction and industry must have a special protective coating that will protect their inner and outer surfaces from the negative effects of environmental factors. And in particular, pipes made of steel alloys need protection against corrosion. What materials create the internal anti-corrosion coating of pipes - we will try to understand this article in detail.

Why is it important to protect steel products from corrosion?

Corrosion or rusting is a special physical and chemical process in which the material actively interacts with the external environment.

During this interaction, reactions occur that change the quality and properties of the material. Under the influence of rusting processes, the metal is gradually destroyed and the steel alloy product itself gradually becomes unusable, which is why the timely application of an anti-corrosion coating of pipes is so important.

Types and properties of coatings against corrosion

To protect the material from the rusting process, various types of anti-corrosion special coatings can be used. The most popular among the compositions of this variety are paints, enamels and primers. These substances have a number of advantages:

1. They can process products of large dimensions and components of complex shapes;
2. Primers, enamels and paints that provide protection against rust are applied to the metal surface quickly and easily;
3. The funds are economical in consumption, they can be used during repair work, without stopping the operation of the pipeline;
4. Paints, primers and enamels are sold at an affordable price and in a huge assortment.

In addition, the use of these substances allows you to get a certain color of the outer coating.

Popular brands of compounds

The production of pipes with anti-corrosion coating is the main activity of many modern industrial enterprises. For the protective treatment of products, manufacturers use a variety of compositions. Let's get acquainted with the most popular brands:

1. "Nerzhamet" is a special anti-corrosion enamel that is applied to clean surfaces of newly manufactured products, but it is also possible to use the substance in the repair of pipelines and treat elements already covered with rust;
2. "Nerzhaluks" - this coloring composition is valued by professionals for a high degree of adhesion and the possibility of application on different surfaces. For example, it is possible to process aluminum, brass, titanium, copper and zinc surfaces with it;
3. Paint "Cycrol" is used for processing pipes made of galvanized steel;
4. The composition with the name "Phosphorgrunt" is used in the process of anti-corrosion treatment of products made of ferrous and non-ferrous metals.

There are also compounds with silver, plastic, modifiers that convert rust.

For the protective treatment of pipeline elements, the following compositions are more often used: Nerzhakhim, Polyurethol, Epostat, Zinconol and Urizol. Let's talk about the advantages of the latter type of anti-corrosion protection in more detail.

Features of using a protective coating Urizol

Steel pipe with anti-corrosion coating Urizol is most often used in pipelines intended for the transportation of oil and its derivatives, natural gas. The composition necessarily processes all elements: nodes, fittings, connection details. Urizol treatment helps protect system elements from various types of corrosion - atmospheric and underground.

The unequivocal advantage of this protective composition is the ease of application. A special spray device is used to treat tubular elements, and as soon as the substance hits the metal surface, a chemical reaction will begin, as a result of which a sufficiently thick and reliable protective coating is formed on the metal.

It is important to know that in the oil industry, as well as in some other areas of communications construction, pipes with internal and external anti-corrosion coatings must be used. Protective painting of the inner walls of pipe components is carried out with epoxy compounds and in the factory!

The mandatory anti-corrosion treatment of pipeline parts is prescribed in SNiP 2.03.11-85.

How is the anti-corrosion treatment process carried out?

To begin with, we note that the anti-corrosion treatment of pipe surfaces is not an easy task, requiring compliance with many nuances. Preparations for work begin with a visual inspection of all elements of the system that need to be coated with a protective compound.

Attention! The condition of pipes and other elements that need protection against rust should be assessed exclusively by specialists. Professionals will accurately determine the extent to which the surface is damaged, as well as make an estimate for the work and purchase of the necessary materials. In choosing an anti-corrosion composition, specialists will start from many factors: the temperature regime at which the system is operated, the material for the manufacture of elements, the specifics of the use of the pipeline.

Before the process of directly applying the composition to the surface, it must be carefully cleaned. All types of dirt, old paint must be removed from it. Next, the surface of the treated structure is degreased with a special hydrocarbon-based solvent.

Next, proceed to the processing of the protective composition. Different compositions are applied under different conditions, and are also prepared in the right proportions immediately before the application procedure. The protective layer is applied in several layers, and at the same time, each previous layer of the coating must dry.

After the required number of layers is applied, a control inspection of the pipeline and its elements is carried out. To determine the quality of the work done, special equipment is used (photo) and upon inspection, an act is drawn up confirming the performance of the work.

10.1. When designing means of protecting steel pipelines (underground, surface, above-ground and underwater with deepening into the bottom) from underground and atmospheric corrosion, one should be guided by the requirements of GOST 25812-83 * and regulatory documents approved in the prescribed manner.

10.2. Anti-corrosion protection, regardless of the method of laying pipelines, must ensure their trouble-free (due to corrosion) operation during the operational period.

10.3. Protection of pipelines (with the exception of aboveground ones) from underground corrosion, regardless of the corrosiveness of the soil and the area of ​​​​their laying, should be carried out in a complex way: protective coatings and electrochemical protection means.

10.4. Depending on the specific conditions of laying and operation of pipelines, two types of protective coatings should be used: reinforced and normal.

The reinforced type of protective coatings should be used on pipelines of liquefied hydrocarbons, pipelines with a diameter of 1020 mm or more, regardless of the laying conditions, as well as on pipelines of any diameter laid:

south of 50°N;

in saline soils of any region of the country (saline, solonetzes, solods, takyrs, sors, etc.);

in swampy, swampy, chernozem and irrigated soils, as well as in areas of promising watering;

at underwater crossings and in floodplains, as well as at crossings over railways and roads, including on protective cases and on sections of pipelines adjacent to them, within the distances established during design, in accordance with Table 3 and 4;

at intersections with various pipelines - 20 m on both sides of the intersection;

in areas of industrial and domestic wastewater, garbage and slag dumps;

in areas of stray currents;

in sections of pipelines with a temperature of the transported product of 313K (40 ° C) and above;

in sections of oil pipelines, oil product pipelines laid at a distance of less than 1000 m from rivers, canals, lakes, reservoirs, as well as the boundaries of settlements and industrial enterprises.

In all other cases, protective coatings of the normal type are used.

10.5. Pipelines with above-ground laying must be protected from atmospheric corrosion by paint and varnish, glass-enamel, metal coatings or coatings of greases.

10.6. Paint coatings must have a total thickness of at least 0.2 mm and a continuity of at least 1 kV per thickness.

The control of paint coatings should be carried out: by thickness with a thickness gauge of the MT-41NTs type (TU 25-06.2500-83), and by continuity - with a spark flaw detector of the LKD-1m type or the Krona-1R type (TU 25-06.2515-83).

10.7. The thickness of glass-enamel coatings (OST 26-01-1-90) must be at least 0.5 mm, continuity - at least 2 kV per thickness.

Note. Control of glass-enamel coatings should be carried out with the devices specified in clause 10.6.

10.8. Lubricating greases should be used in areas with an air temperature of at least minus 60 °C in areas with a temperature of operation of pipelines not higher than plus 40 °C.

The grease coating should contain 20% (by weight) PAK-Z or PAK-4 aluminum powder and be between 0.2 and 0.5 mm thick.

10.9. Corrosion protection of supports and other metal structures of above-ground pipelines should be carried out in accordance with the requirements of SNiP III-23-81 *.

10.10. In conditions of increased corrosion hazard: in salt marshes with soil resistance up to 20 Ohm?m, in areas where the groundwater level is above the lower generatrix of the pipeline for at least 6 months a year, and in areas with a pipeline operating temperature of plus 40 ° C and above, , as a rule, redundancy of means of electrochemical protection.

10.11. Protective ground loops of process equipment located at CS, GDS, PS and other similar sites should not have a shielding effect on the electrochemical protection system of underground utilities.

10.12. As down conductors of grounding devices, as a rule, protectors should be used, the number of which is determined by calculation, taking into account the service life and the permissible value of the spreading resistance of protective grounding, determined by the PUE, approved by the USSR Ministry of Energy.

10.13. The installation of anode grounds and protectors should be provided below the freezing depth of the soil in places with a minimum resistivity.

10.14. In places where the drain cable is connected to the anode ground, an identification mark should be provided.

10.15. The drain cable or connecting wire to the anode earth should be designed for the maximum current of the cathode plant and this calculation checked against the allowable voltage drop.

10.16. When non-factory anode grounding is used for electrochemical protection, the connection of electrodes should be provided with a cable with a cross section of at least 6 mm2 (for copper).

10.17. When designing anode grounds with coke filling, the granulation of coke breeze should be no more than 10 mm.

10.18. All contact connections in electrochemical protection systems, as well as cable connection points to the pipeline and anodic grounding, must be insulated with reliability and durability not lower than those accepted by the factory for insulating connecting cables.

10.19. In the areas of underground laying of the connecting cable in the anode grounding-cathodic protection installation-pipeline circuit, it is necessary to provide for the use of a cable with two-layer polymer insulation only.

10.20. Power supply of installations of cathodic protection of pipelines should be carried out according to category II from existing power lines with a voltage of 0.4; 6.0; 10.0 kV or designed along the route power lines or autonomous sources.

10.21. The power quality indicators of cathodic protection installations must comply with the requirements of GOST 13109-87.

10.22. Electrochemical protection of cables for technological connection of pipelines should be designed in accordance with GOST 9.602-89

10.23. For underground and surface pipelines laid in areas of permafrost, electrochemical protection should be provided, regardless of the corrosive activity of the soil.

10.24. Cathodic protection should be used for pipelines around which the soil freezes in winter ("cold" sections).

10.25. In the absence of sources of electricity, it is allowed to use extended protectors instead of cathode stations in "cold" sections.

10.26. Protector protection (including extended protectors) can be used on any sections of the pipeline where the soil around it is in a thawed state.

10.27. In cathodic protection installations, extended, pile and deep anode grounding should be used.

10.28. The estimated service life of extended and piled anode groundings should be at least 10, and deep - at least 20 years.

10.29. The minimum protective potential at the temperature of the soil (in the range of positive temperatures not lower than plus 1°C), in which the pipeline is located, should be determined by the formula

, (63)

In the temperature range of the transported product from minus 5 to minus 1°C Umint=Umin1°C, and in the temperature range of ±1°C Umint= -0.85 V.

10.30. Pipelines, the temperature of the walls and soil around which during operation does not exceed minus 5 °C, are not subject to electrochemical protection.