The problem of protecting metals from corrosion arose almost at the very beginning of their use. People tried to protect metals from atmospheric action with the help of grease, oils, and later coating with other metals and, above all, low-melting tin (tinning). In the writings of the ancient Greek historian Herodotus (5th century BC), there is already a mention of the use of tin to protect iron from corrosion. The task of chemists has been and remains to elucidate the essence of corrosion phenomena, to develop measures that prevent or slow down its course. Corrosion of metals is carried out in accordance with the laws of nature and therefore it cannot be completely eliminated, but can only be slowed down. There is a way to reduce the corrosion of metals, which cannot be strictly attributed to protection - this is metal alloying, i.e. receiving alloys. For example, at present, a large number of stainless steels have been created by adding nickel, chromium, cobalt, etc. to iron. Such steels, indeed, do not rust, but their surface corrosion, although at a low rate, does take place. It turned out that with the addition of alloying additives, the corrosion resistance changes abruptly. A rule has been established according to which a sharp increase in the corrosion resistance of iron is observed when an alloying additive is introduced in an amount of 1/8 atomic fraction, i.e. one dopant atom per eight iron atoms. It is believed that with such a ratio of atoms, their ordered arrangement in the crystal lattice of the solid solution occurs, which hinders corrosion. One of the most common ways to protect metals from corrosion is the application of protective films on their surface: varnish, paint, enamel, and other metals. Paint coatings are most accessible to a wide range of people. Varnishes and paints have low gas and vapor permeability, water-repellent properties and therefore prevent access to the metal surface of water, oxygen and aggressive components contained in the atmosphere. Coating the surface of the metal with a paint layer does not exclude corrosion, but serves only as a barrier for it, which means it only slows down corrosion. Therefore, the quality of the coating is important - layer thickness, continuity (porosity), uniformity, permeability, ability to swell in water, adhesion strength (adhesion). The quality of the coating depends on the thoroughness of surface preparation and the method of applying the protective layer. Scale and rust must be removed from the surface of the coated metal. Otherwise, they will prevent good adhesion of the coating to the metal surface. Poor coating quality is often associated with increased porosity. It often occurs during the formation of a protective layer as a result of solvent evaporation and the removal of curing and degradation products (during film aging). Therefore, it is usually recommended to apply not one thick layer, but several thin layers of the coating. In many cases, an increase in the thickness of the coating leads to a weakening of the adhesion of the protective layer to the metal. Air cavities and bubbles cause great harm. They are formed when the quality of the coating operation is poor. To reduce water wettability, paint coatings are sometimes, in turn, protected with wax compounds or organosilicon compounds. Lacquers and paints are most effective in protecting against atmospheric corrosion. In most cases, they are unsuitable for the protection of underground structures and structures, since it is difficult to prevent mechanical damage to the protective layers upon contact with the ground. Experience shows that the service life of paintwork under these conditions is short. It turned out to be much more practical to use thick coatings of coal tar (bitumen).

In some cases, paint pigments also act as corrosion inhibitors. These pigments include chromates of strontium, lead and zinc (SrCrO 4 , PbCrO 4 , ZnCrO 4).

Often a layer of primer is applied under the paint layer. The pigments included in its composition must also have inhibitory properties. As the water passes through the primer layer, it dissolves some of the pigment and becomes less corrosive. Among the pigments recommended for soils, red lead Pb3O4 is recognized as the most effective.

Instead of a primer, phosphate coating of the metal surface is sometimes carried out. To do this, solutions of iron (III), manganese (II) or zinc (II) orthophosphates containing orthophosphoric acid H3PO4 itself are applied to a clean surface with a brush or spray gun. In our country, for this purpose, a 3% solution of a mixture of acid salts Fe (H 2 PO 4) 3 and Mn (H 2 PO 4) 2 with the addition of KNO 3 or Cu (NO 3) 2 as accelerators is used. Under factory conditions, phosphating is carried out at 97…99 0 C for 30…90 min. The metal dissolving in the phosphated mixture and the oxides remaining on its surface contribute to the formation of the phosphate coating.

Several different preparations have been developed for phosphating the surface of steel products. Most of them consist of mixtures of manganese and iron phosphates. Perhaps the most common drug is "mazhef" - a mixture of manganese dihydrophosphates Mn (H 2 PO 4) 2, iron Fe (H 2 PO 4) 2 and free phosphoric acid. The name of the drug consists of the first letters of the components of the mixture. In appearance, majef is a finely crystalline powder of white color with a ratio between manganese and iron from 10:1 to 15:1. It consists of 46…52% P2O5; not less than 14% Mn; 0.3…3.0% Fe. When phosphatizing with mazhef, a steel product is placed in its solution, heated to approximately 100 0 C. In the solution, iron dissolves from the surface with the release of hydrogen, and a dense, durable and poorly soluble in water protective layer of gray-black manganese and iron phosphates is formed on the surface. When the layer thickness reaches a certain value, further dissolution of iron stops. A film of phosphates protects the surface of the product from atmospheric precipitation, but is not very effective against salt solutions and even weak acid solutions. Thus, the phosphate film can only serve as a primer for the subsequent application of organic protective and decorative coatings - varnishes, paints, resins. Phosphating process lasts 40…60 min. To accelerate phosphating, 50...70 g/l of zinc nitrate is introduced into the solution. In this case, the phosphating time is reduced by 10...12 times.

In production conditions, an electrochemical method is also used - treatment of products with alternating current in a solution of zinc phosphate at a current density of 4 A / dm 2 and a voltage of 20 V and at a temperature of 60 ... By themselves, phosphate coatings do not provide reliable corrosion protection. They are mainly used as a base for painting, providing good adhesion of paint to metal. In addition, the phosphate layer reduces corrosion damage caused by scratches or other defects.

To protect metals from corrosion, vitreous and porcelain enamels are used - silicate coatings, the thermal expansion coefficient of which should be close to that of the coated metals. Enameling is carried out by applying an aqueous suspension to the surface of the products or by dry powdering. First, a primer layer is applied to the cleaned surface and fired in a kiln. Next, a layer of integumentary enamel is applied and the firing is repeated. The most common vitreous enamels are transparent or muted. Their components are SiO 2 (basic mass), B 2 O 3 , Na 2 O, PbO. In addition, auxiliary materials are introduced: oxidizers of organic impurities, oxides that promote the adhesion of enamel to the surface to be enameled, silencers, dyes. The enameling material is obtained by fusing the initial components, grinding into powder and adding 6 ... 10% clay. Enamel coatings are mainly applied to steel, but also to cast iron, copper, brass and aluminum.

Enamels have high protective properties, which are due to their impermeability to water and air (gases) even with prolonged contact. Their important quality is high resistance at elevated temperatures. The main disadvantages of enamel coatings include sensitivity to mechanical and thermal shocks. With prolonged use, a network of cracks may appear on the surface of enamel coatings, which provides access to moisture and air to the metal, as a result of which corrosion begins.

Cement coatings are used to protect cast iron and steel water pipes from corrosion. Since the coefficients of thermal expansion of Portland cement and steel are close, and the cost of cement is low, it is quite widely used for these purposes. The disadvantage of Portland cement coatings is the same as enamel coatings - high sensitivity to mechanical shocks.

A common way to protect metals from corrosion is to coat them with a layer of other metals. The coating metals themselves corrode at a low rate, as they are covered with a dense oxide film. The coating layer is applied by various methods: short-term immersion in a bath of molten metal (hot coating), electrodeposition from aqueous electrolyte solutions (galvanic coating), spraying (metallization), powder treatment at elevated temperature in a special drum (diffusion coating), using a gas-phase reaction , for example 3CrCl 2 + 2Fe - > 2FeCl 3 + 3Cr (in an alloy with Fe).

There are other methods for applying metal coatings, for example, a kind of diffusion method for protecting metals is immersing products in a calcium chloride CaCl 2 melt, in which the applied metals are dissolved.

In production, chemical deposition of metal coatings on products is widely used. The chemical metal plating process is catalytic or autocatalytic, and the surface of the product is the catalyst. The solution used for plating contains the compound of the deposited metal and the reducing agent. Since the catalyst is the surface of the product, the release of metal occurs precisely on it, and not in the volume of the solution. In autocatalytic processes, the catalyst is a metal deposited on the surface. At present, methods have been developed for the chemical coating of metal products with nickel, cobalt, iron, palladium, platinum, copper, gold, silver, rhodium, ruthenium, and some alloys based on these metals. Hypophosphite and sodium borohydride, formaldehyde, hydrazine are used as reducing agents. Naturally, chemical nickel plating can not apply a protective coating on any metal. Most often, copper products are subjected to it.

Metal coatings are divided into two groups: corrosion-resistant and protective. For example, for the coating of iron-based alloys, the first group includes nickel, silver, copper, lead, chromium. They are more electropositive with respect to iron; in the electrochemical series of voltages, metals are to the right of iron. The second group includes zinc, cadmium, aluminum. With respect to iron, they are more electronegative; in a series of stresses are located to the left of iron.

In everyday life, a person most often encounters iron coatings with zinc and tin. Sheet iron plated with zinc is called galvanized iron, and plated with tin is called tinplate. The first is used in large quantities on the roofs of houses, and tin cans are made from the second. Both are obtained mainly by pulling a sheet of iron through a melt of the corresponding metal. For greater durability, water pipes and fittings made of steel and gray cast iron are often galvanized also by dipping into the melt of this metal. This dramatically increases their service life in cold water. Interestingly, in warm and hot water, the service life of galvanized pipes can be even less than that of non-galvanized ones.

Tests have shown that galvanized sheet with a coating thickness of 0.03 mm, which corresponds to 0.036 g / cm 2 when coated on both sides, lasts about 8 years on the roofs of houses. In an industrial atmosphere (in the atmosphere of big cities), it also serves only four years. This reduction in service life is due to exposure to sulfuric acid contained in the air of cities.

Coatings of zinc and tin (as well as other metals) protect iron from corrosion while maintaining continuity. If the coating layer is broken (cracks, scratches), the corrosion of the product proceeds even more intensively than without coating. This is due to the "work" of the galvanic element iron - zinc and iron - tin. Cracks and scratches are filled with moisture and solutions are formed. Since zinc is more electronegative than iron, its ions will preferentially go into solution, and the remaining electrons will flow to the more electropositive iron, making it the cathode.

Hydrogen ions (water) will approach the iron cathode and discharge, accepting electrons. The resulting hydrogen atoms combine to form an H2 molecule. Thus, the ion flows will be separated and this facilitates the flow of the electrochemical process. The zinc coating will be exposed to dissolution (corrosion), and the iron will be protected for the time being. Zinc electrochemically protects iron from corrosion. The protective method of corrosion protection of metal structures and apparatus is based on this principle.

In the presence of moisture, or rather in the presence of an electrolyte, a galvanic cell will begin to operate. A more electronegative metal will dissolve in it, and the structure or apparatus will be cathodically protected. The protection will operate until the anode, a more electronegative metal, is completely dissolved.

Cathodic protection of metals against corrosion is very similar to tread protection. We can say that cathodic protection is a modification of sacrificial protection. In this case, the structure or hull of the ship is connected to the cathode of a direct current source and thereby protected from dissolution.

In the presence of defects on tinplate, the corrosion process is significantly different than that of galvanized iron. Since tin is more electropositive than iron, iron undergoes dissolution, and tin becomes the cathode. As a result, during corrosion, the tin layer is preserved, and under it, iron actively corrodes.

It is believed that the application of tin to the surface of metals (tinning) was already mastered in the Bronze Age. This was facilitated by the low melting point of tin. In the past, tinning of copper and brass utensils was especially often carried out: basins, boilers, jugs, samovars, etc. Tin corrosion products are harmless to humans, so tinned utensils were widely used in everyday life. In the XV century. in many European countries (Germany, Austria, Holland, England and France), tableware made of tin was widely used. There is evidence that in the ore mountains of Bohemia, tin spoons, cups, jugs, and plates began to be made as early as the 12th century.

Tinned iron is still used in large quantities for the manufacture of food storage containers (tin cans). However, aluminum foil has been increasingly used for this purpose in recent years. Zinc and galvanized iron utensils are not recommended for food storage. Despite the fact that metallic zinc is covered with a dense oxide film, it still undergoes dissolution. Although zinc compounds are relatively mildly toxic, they can be harmful in large quantities.

Modern technology includes parts and structures made of various metals and alloys. If they are in contact and get into an electrolyte solution (sea water, solutions of any salts, acids and alkalis), then a galvanic cell can form. The more electronegative metal becomes the anode, and the more electropositive the cathode. The generation of current will be accompanied by the dissolution (corrosion) of the more electronegative metal. The greater the difference in the electrochemical potentials of the contacting metals, the greater the corrosion rate.

The use of inhibitors is one of the most effective ways to combat corrosion of metals in various aggressive environments (atmospheric, in sea water, in cooling liquids and salt solutions, under oxidizing conditions, etc.). Inhibitors are substances capable of slowing down or stopping chemical processes in small quantities. Inhibitors interact with intermediate products of the reaction or with active sites on which chemical transformations occur. They are very specific for each group of chemical reactions. Corrosion of metals is just one of the types of chemical reactions that are amenable to the action of inhibitors. According to modern concepts, the protective effect of inhibitors is associated with their adsorption on the surface of metals and inhibition of anodic and cathodic processes.

The first inhibitors were found by chance, by experience, and often became a clan secret. It is known that Damascus craftsmen used solutions of sulfuric acid with the addition of brewer's yeast, flour, and starch to remove scale and rust. These impurities were among the first inhibitors. They did not allow the acid to act on the weapon metal, as a result of which only scale and rust were dissolved.

Inhibitors, without knowing it, have long been used in Russia. To combat rust, Ural gunsmiths prepared "pickle soups" - solutions of sulfuric acid, to which flour bran was added. One of the simplest inhibitors of atmospheric corrosion of metals is sodium nitrite NaNO2. It is used in the form of concentrated aqueous solutions, as well as solutions thickened with glycerin, hydroxyethylcellulose or carboxymethylcellulose. Sodium nitrite is used to preserve steel and cast iron products. For the first apply. 25% aqueous solutions, and for the second - 40%. After processing (usually by dipping in solutions), the products are wrapped in paraffin paper. Thickened solutions have the best effect. The shelf life of products treated with thickened solutions increases by 3...4 times compared to aqueous solutions.

According to 1980 data, the number of corrosion inhibitors known to science exceeded 5,000. It is believed that 1 ton of inhibitor saves about 5,000 rubles in the national economy.

Corrosion control is of great national economic importance. This is a very fertile area for the application of strength and abilities.

Corrosion- a spontaneous process and, accordingly, proceeding with a decrease in the Gibbs energy of the system. The chemical energy of the reaction of the corrosion destruction of metals is released in the form of heat and dissipated in the surrounding space.

Corrosion leads to large losses as a result of the destruction of pipelines, tanks, metal parts of machines, ship hulls, offshore structures, etc. The irretrievable loss of metals from corrosion is 15% of their annual output. The goal of corrosion control is to conserve metal resources, the world's reserves of which are limited. The study of corrosion and the development of methods for protecting metals from it are of theoretical interest and are of great economic importance.

The rusting of iron in air, the formation of scale at high temperatures, the dissolution of metals in acids are typical examples of corrosion. As a result of corrosion, many properties of metals deteriorate: strength and ductility decrease, friction between moving parts of machines increases, and the dimensions of parts are violated. Distinguish between chemical and electrochemical corrosion.

Chemical, corrosion– destruction of metals by their oxidation in dry gases, in non-electrolyte solutions. For example, the formation of scale on iron at high temperature. In this case, the oxide films formed on the metal often prevent further oxidation, preventing further penetration of both gases and liquids to the metal surface.

electrochemical corrosion called the destruction of metals under the action of emerging galvanic pairs in the presence of water or another electrolyte. In this case, along with the chemical process - the release of electrons by metals, an electrical process also takes place - the transfer of electrons from one area to another.

This type of corrosion is divided into separate types: atmospheric, soil, corrosion under the action of "stray" current, etc.

Electrochemical corrosion is caused by impurities contained in the metal, or the heterogeneity of its surface. In these cases, when the metal comes into contact with the electrolyte, which can also be moisture adsorbed in air, many microgalvanic cells appear on its surface. . Anodes are metal particles cathodes– impurities and metal areas with a more positive electrode potential. The anode dissolves and hydrogen is released at the cathode. At the same time, the reduction of oxygen dissolved in the electrolyte is possible at the cathode. Therefore, the nature of the cathodic process will depend on some conditions:

acidic environment: 2H + + 2ē \u003d H 2 (hydrogen depolarization),

О 2 + 4Н + + 4ē → 2Н 2 О

neutral environment: O 2 +2H 2 O+4e - \u003d 4OH - (oxygen depolarization).

As an example, consider atmospheric corrosion iron in contact with tin. The interaction of metals with a drop of water containing oxygen leads to the appearance of a microvoltaic cell, the circuit of which has the form

(-)Fe|Fe 2+ || O 2 , H 2 O| sn (+).

The more active metal (Fe) is oxidized, donating electrons to copper atoms and goes into solution in the form of ions (Fe 2+). Oxygen depolarization occurs at the cathode.

Corrosion protection methods. All methods of corrosion protection can be divided into two large groups: non-electrochemical(alloying of metals, protective coatings, changing the properties of a corrosive environment, rational design of products) and electrochemical(project method, cathodic protection, anode protection).

Alloying of metals- this is an effective, albeit expensive, method of increasing the corrosion resistance of metals, in which components are introduced into the alloy composition that cause passivation of the metal. Chromium, nickel, titanium, tungsten, etc. are used as such components.

Protective coatings- these are layers artificially created on the surface of metal products and structures. The choice of coating type depends on the conditions in which the metal is used.

Materials for metal protective coatings can be pure metals: zinc, cadmium, aluminum, nickel, copper, tin, chromium, silver and their alloys: bronze, brass, etc. According to the nature of the behavior of metal coatings during corrosion, they can be divided into cathodic(for example, on steel Cu, Ni, Ag) and anode(zinc on steel). Cathodic coatings can protect the metal from corrosion only in the absence of pores and damage to the coating. In the case of anodic coating, the metal to be protected plays the role of a cathode and therefore does not corrode. However, the potentials of metals depend on the composition of the solutions; therefore, when the composition of the solution changes, the nature of the coating may also change. Thus, the coating of steel with tin in a solution of H 2 SO 4 is cathodic, and in a solution of organic acids it is anodic.

Non-metallic protective Coatings can be either inorganic or organic. The protective effect of such coatings is reduced mainly to the isolation of the metal from the environment.

Electrochemical protection method based on the inhibition of anodic or cathodic reactions of the corrosion process. Electrochemical protection is carried out by connecting to the protected structure (ship hull, underground pipeline), located in the electrolyte environment (sea, soil water), a metal with a more negative value of the electrode potential - protector.

Corrosion has a destructive effect on metal products and alloys. When interacting with the environment, metal products become stained in the form of rust. The more active the metal, the more susceptible it is to corrosion.

Corrosion has a destructive effect on cars, ships, communications and other metal products, which can lead to oil and gas leakage and other negative consequences. It adversely affects human health, and oxidation products pollute the environment.

Corrosion is unacceptable in the aviation, chemical and nuclear industries. Sometimes the cost of repairing metal products exceeds the cost of the material that was spent on their manufacture.

Main types of corrosion processes

Types of corrosion of metals can be divided according to the following features: the nature of destruction, the corrosive environment and the mechanism of action.

Based on the nature of the damage, corrosion can be:

• solid. At the same time, it can be uniform and uneven. When uniform, the entire surface of the product is destroyed. When uneven, spots and punctate depressions appear;
• intergranular. In this case, it penetrates deep into the product along the boundaries of metal grains;
• transcrystalline, while the metal is cut by a crack through the grain;
• electoral. There is a destruction of one of the components of the alloy. For example, zinc can degrade in brass.
• subsurface. It starts at the surface and gradually penetrates into the upper layers of the metal.

There are the following types of corrosive environment:

• atmosphere;
• the soil;
• liquid (alkali, acid or saline solutions).

The mechanism of action divides corrosion into chemical and electrochemical.

Chemical corrosion is a process in which the spontaneous destruction of metals occurs. It occurs when metal products interact with an actively corrosive medium, most often gas. These processes are accompanied by high temperatures.

As a result, the metal is simultaneously oxidized and the corrosive medium is restored. Chemical corrosion also occurs when interacting with organic liquids, for example, with petroleum products, alcohol, etc.

Electrochemical corrosion occurs in electrolytes, for example, in aqueous solutions. The electrochemical reaction causes an electric current, which contributes to the destruction of the metal. In this case, both chemical processes occur, in which electrons are released, and electrical, in which electrons move.

Destruction occurs when dissimilar metals come into contact. Therefore, metals that contain a lot of impurities are more susceptible to destruction.

The heterogeneity of the structure of the metal leads to the fact that during electrochemical corrosion, cathode-anode pairs are formed according to the laws of electroplating. If metal products differ from each other in chemical composition, then a layer of rust forms on the surface of metal products.

This corrosion is most often the cause of the destruction of metals. The figures below show the mechanism of action of electrochemical corrosion.

In the external environment, metal products are most actively affected by oxygen, high humidity, oxides of sulfur, nitrogen, carbon dioxide, and groundwater. Salt water speeds up the oxidation process, which is why sea boats rust faster than river boats.

It is impossible to stop this natural process, it remains only to find ways to protect against corrosion. True, it is impossible to completely get rid of the corrosion process, but these methods help to slow down the process itself.

Methods for resisting corrosion processes

To protect metals from corrosion, there are the following methods:

• increasing the resistance of metals by increasing the chemical composition;
• isolation of metal coatings from aggressive environmental influences;
• reducing the aggressiveness of the environment in which the operation of metal products;
• electrochemical, which, thanks to the laws of electroplating, reduce corrosion processes.

These methods can be divided into two large groups. The first two methods are applied before metal products are used, that is, at the stage of their production. At the same time, certain structural materials are selected for the production of the product, various galvanic and protective coatings are applied.

The last two methods are used in the operation of metal products. At the same time, for protection, a current is passed through the product, the aggressiveness of the environment is reduced by adding various inhibitors, so the product itself is not pre-treated before operation.

Methods for increasing resistance

These protection methods are based on the creation of alloys that have anti-corrosion properties. Components are added to the metal to increase its corrosion resistance. An example is the alloying of steel with chromium.

The method is used in the manufacture of steel. The result is chromium stainless steels that are resistant to corrosion. Increase the anti-corrosion characteristics of steels with the addition of nickel, copper and cobalt.

Rust does not appear on these surfaces, but corrosion is present. Corrosion is slowed down due to the fact that one atom of an alloying additive is added to eight iron atoms, and this orders the arrangement of atoms in the crystal lattice of the solid solution, which prevents corrosion.

Corrosion resistance can be improved by removing impurities from metals or alloys that accelerate corrosion. For example, iron is removed from magnesium or aluminum alloys, sulfur from iron alloys, and so on.

Reducing the aggressiveness of the environment and electrochemical protection

Reducing the aggressiveness of the external environment is achieved by removing from it substances that are depolarizers, or by isolating metals from the depolarizer. The removal of oxygen from the environment is called deoxidation.

To slow down the corrosion process, special substances are introduced into the environment - inhibitors. They can be either organic or inorganic. Inhibitor molecules are absorbed by the metal surface and, thereby, contribute to a sharp decrease in the rate of metal dissolution and prevent the occurrence of electrode processes.

During electrochemical protection with the help of an external electric current that passes through the metal, the potential of the metal is shifted and, thereby, its corrosion rate changes.

Depending on the potential shift, electrochemical protection can be cathodic and anodic. These methods are used to protect drilling platforms, welded metal bases, underground pipelines, and also protect the underwater parts of ships.

Film protection

In order to protect metal products from corrosion, a protective coating can be applied. As a coating, you can use varnishes, paints, enamels, plastics, etc.

Paint coatings are easy to apply, inexpensive, have water-repellent properties, do not react chemically with metal, fill pores and cracks well. They serve to protect metals from environmental components that cause corrosion processes.

If you choose the right paints and varnishes and follow the technology of their application, they can serve as a coating for up to 5 years.

Often a primer is applied under the paintwork, passing through which the water dissolves some pigments and becomes less corrosive. Instead of a primer, the surface can be phosphated. They are applied with a brush or spray. For steel products, most of these preparations consist of mixtures of manganese and iron phosphates.

You can protect a metal product by applying a layer of metal that is more corrosion resistant. In this case, corrosion destroys the coating itself. Such metals are chromium, nickel, zinc. For example, iron is coated with chromium.

These methods can be divided into 2 groups. The first 2 methods are usually implemented before the start of the production operation of a metal product (the choice of structural materials and their combinations at the stage of designing and manufacturing a product, applying protective coatings to it). The last 2 methods, on the contrary, can be carried out only during the operation of the metal product (passing current to achieve a protective potential, introducing special additives-inhibitors into the technological environment) and are not associated with any pre-treatment prior to use.

The second group of methods allows, if necessary, to create new protection modes that provide the least corrosion of the product. For example, in certain sections of the pipeline, depending on the aggressiveness of the soil, it is possible to change the density of the cathode current. Or for different grades of oil pumped through pipes, use different inhibitors.

Q: How are corrosion inhibitors applied?

Answer: To combat the corrosion of metals, corrosion inhibitors are widely used, which are introduced in small quantities into an aggressive environment and create an adsorption film on the metal surface, which slows down electrode processes and changes the electrochemical parameters of metals.

Question: What are the ways to protect metals from corrosion using paints and varnishes?

Answer: Depending on the composition of the pigments and the film-forming base, paint coatings can act as a barrier, passivator or protector.

Barrier protection is the mechanical isolation of a surface. Violation of the integrity of the coating, even at the level of the appearance of microcracks, predetermines the penetration of an aggressive medium to the base and the occurrence of under-film corrosion.

Passivation of the metal surface with the help of LCP is achieved by chemical interaction of the metal and coating components. This group includes primers and enamels containing phosphoric acid (phosphating), as well as compositions with inhibitory pigments that slow down or prevent the corrosion process.

Metal protector protection is achieved by adding powder metals to the coating material, which create donor electron pairs with the protected metal. For steel, these are zinc, magnesium, aluminum. Under the action of an aggressive environment, the additive powder gradually dissolves, and the base material does not corrode.

Question: What determines the durability of metal protection against corrosion by paints and varnishes?

Answer: Firstly, the durability of metal protection against corrosion depends on the type (and kind) of the applied paintwork. Secondly, the decisive role is played by the thoroughness of the preparation of the metal surface for painting. The most time-consuming process in this case is the removal of corrosion products formed earlier. Special compounds are applied that destroy rust, followed by their mechanical removal with metal brushes.

In some cases, rust removal is almost impossible to achieve, which implies the widespread use of materials that can be applied directly to surfaces damaged by corrosion - rust coatings. This group includes some special primers and enamels used in multi-layer or independent coatings.

Question: What are highly filled two-component systems?

Answer: These are anti-corrosion paints and varnishes with a reduced solvent content (the percentage of volatile organic substances in them does not exceed 35%). In the market for home use materials, one-component materials are mainly offered. The main advantage of highly filled systems compared to conventional systems is significantly better corrosion resistance with a comparable layer thickness, lower material consumption and the possibility of applying a thicker layer, which ensures that the necessary anticorrosion protection is obtained in just 1-2 times.

Question: How to protect the surface of galvanized steel from destruction?

Answer: Solvent-based anticorrosive primer based on modified vinyl-acrylic resins "Galvaplast" is used for interior and exterior works on bases made of ferrous metals with scale removed, galvanized steel, galvanized iron. The solvent is white spirit. Application - brush, roller, spray. Consumption 0.10-0.12 kg / sq.m; drying 24 hours.

Q: What is patina?

Answer: The word "patina" refers to a film of various shades that forms on the surface of copper and copper-containing alloys under the influence of atmospheric factors during natural or artificial aging. Patina is sometimes referred to as oxides on the surface of metals, as well as films that cause tarnishing over time on the surface of stones, marble or wooden objects.

The appearance of a patina is not a sign of corrosion, but rather a natural protective layer on the copper surface.

Question: Is it possible to artificially create a patina on the surface of copper products?

Answer: Under natural conditions, a green patina is formed on the surface of copper within 5-25 years, depending on the climate and the chemical composition of the atmosphere and precipitation. At the same time, copper carbonates are formed from copper and its two main alloys - bronze and brass: bright green malachite Cu 2 (CO 3) (OH) 2 and azure blue azurite Cu 2 (CO 3) 2 (OH) 2. For zinc-containing brass, the formation of green-blue rosasite of the composition (Cu,Zn) 2 (CO 3) (OH) 2 is possible. Basic copper carbonates can be easily synthesized at home by adding an aqueous solution of soda ash to an aqueous solution of a copper salt, such as copper sulphate. At the same time, at the beginning of the process, when there is an excess of copper salt, a product is formed that is closer in composition to azurite, and at the end of the process (with an excess of soda) - to malachite.

Saving coloring

Question: How to protect metal or reinforced concrete structures from the influence of an aggressive environment - salts, acids, alkalis, solvents?

Answer: To create chemical-resistant coatings, there are several protective materials, each of which has its own area of ​​protection. The widest range of protection has: XC-759 enamels, ELOKOR SB-022 varnish, FLK-2, primers, XC-010, etc. In each individual case, a specific color scheme is selected, according to the operating conditions. Tikkurilla Coatings Temabond, Temacoat and Temachlor paints.

Question: What compositions can be used for painting the internal surfaces of tanks for kerosene and other petroleum products?

Answer: Temaline LP is a two-component epoxy gloss paint with an amino adduct hardener. Application - brush, spray. Drying 7 hours.

EP-0215 ​​is a primer for corrosion protection of the inner surface of caisson tanks operating in a fuel medium with an admixture of water. It is applied on surfaces made of steel, magnesium, aluminum and titanium alloys, operated in various climatic zones, at elevated temperatures and exposed to polluted environment.

Suitable for application of BEP-0261 primer and BEP-610 enamel.

Question: What compositions can be used for the protective coating of metal surfaces in marine and industrial environments?

Answer: Thick-film type paint based on chlorinated rubber is used for painting metal surfaces in marine and industrial environments subject to moderate chemical attack: bridges, cranes, conveyors, port equipment, tank exteriors.

Temacoat HB is a two-component modified epoxy paint used for priming and painting metal surfaces exposed to atmospheric, mechanical and chemical attack. Application - brush, spray. Drying 4 hours.

Question: What compositions should be used to cover difficult-to-clean metal surfaces, including those immersed in water?

Answer: Temabond ST-200 is a two-component modified epoxy paint with aluminum pigmentation and low solvent content. It is used for painting bridges, tanks, steel structures and equipment. Application - brush, spray. Drying - 6 hours.

Temaline BL is a two-component, solvent-free epoxy coating. It is used for painting steel surfaces subject to wear, chemical and mechanical attack when immersed in water, containers for oil or gasoline, tanks and reservoirs, sewage treatment plants. Application - airless spray.

Temazinc is a one component zinc rich epoxy paint with a polyamide hardener. Used as a primer in epoxy, polyurethane, acrylic, chlorinated rubber paint systems for steel and cast iron surfaces exposed to strong atmospheric and chemical attack. It is used for painting bridges, cranes, steel frames, steel structures and equipment. Drying 1 hour.

Question: How to protect underground pipes from fistula formation?

Answer: There can be two reasons for the breakthrough of any pipes: mechanical damage or corrosion. If the first reason is the result of accident and carelessness - the pipe is hooked on something or the weld is broken, then corrosion cannot be avoided, this is a natural phenomenon caused by soil moisture.

In addition to the use of special coatings, there is a protection widely used throughout the world - cathodic polarization. It is a direct current source that provides a polar potential of min 0.85 V, max - 1.1 V. It consists of just a conventional AC voltage transformer and a diode rectifier.

Q: How much does cathodic polarization cost?

Answer: The cost of cathodic protection devices, depending on their design, ranges from 1000 to 14 thousand rubles. A repair team can easily check the polarization potential. Installation of protection is also not expensive and does not involve labor-intensive earthworks.

Protection of galvanized surfaces

Question: Why can't galvanized metals be shot blasted?

Answer: Such preparation violates the natural corrosion resistance of the metal. Surfaces of this kind are treated with a special abrasive agent - round glass particles that do not destroy the protective layer of zinc on the surface. In most cases, it is sufficient to simply treat with an ammonia solution to remove grease stains and zinc corrosion products from the surface.

Question: How to repair a damaged zinc coating?

Answer: Zinc-filled compositions ZincKOS, TsNK, "Vinikor-zinc", etc., which are applied by cold galvanizing and provide anodic protection of the metal.

Question: How is metal protection performed using CNC (zinc-rich compositions)?

Answer: The technology of cold galvanizing with the use of ZNK guarantees absolute non-toxicity, fire safety, heat resistance up to +800°C. The coating of metal with this composition is carried out by spraying, roller or even just a brush and provides the product, in fact, double protection: both cathodic and film. The term of such protection is 25-50 years.

Question: What are the main advantages of the "cold galvanizing" method over hot galvanizing?

Answer: This method has the following advantages:

1. Maintainability.
2. Possibility of drawing in the conditions of a construction site.
3. There are no restrictions on the overall dimensions of protected structures.

Question: At what temperature is thermal diffusion coating applied?

Answer: Application of thermal diffusion zinc coating is carried out at temperatures from 400 to 500°C.

Question: Are there any differences in the corrosion resistance of a coating obtained by thermal diffusion zinc plating compared to other types of zinc coatings?

Answer: The corrosion resistance of thermal diffusion zinc coating is 3-5 times higher than that of galvanized coating and 1.5-2 times higher than the corrosion resistance of hot zinc coating.

Question: What paintwork materials can be used for protective and decorative painting of galvanized iron?

Answer: To do this, you can use both water-based - G-3 primer, G-4 paint, and solvent-based - EP-140, ELOKOR SB-022, etc. Tikkurila Coatings protective systems can be used: 1 Temacoat GPLS-Primer + Temadur, 2 Temaprime EE + Temalac, Temalac and Temadur are tinted according to RAL and TVT.

Question: What kind of paint can gutter and drainage galvanized pipes be painted with?

Answer: Sockelfarg is a black and white water-based latex paint. Designed for application to both new and previously painted outdoor surfaces. Resistant to weather conditions. The solvent is water. Drying 3 hours.

Question: Why are water-based corrosion protection products rarely used?

Answer: There are 2 main reasons: the increased price compared to conventional materials and the opinion in certain circles that water systems have inferior protective properties. However, as environmental legislation tightens, both in Europe and around the world, the popularity of water systems is growing. Experts who tested high-quality water-based materials were able to make sure that their protective properties are not worse than those of traditional materials containing solvents.

Question: What device is used to determine the thickness of the paint film on metal surfaces?

Answer: The most easy-to-use device "Konstanta MK" - it measures the thickness of the paintwork on ferromagnetic metals. Much more functions are performed by the multifunctional thickness gauge "Constant K-5", which measures the thickness of conventional paintwork, galvanic and hot-zinc coatings on both ferromagnetic and non-ferromagnetic metals (aluminum, its alloys, etc.), and also measures surface roughness, temperature and air humidity, etc.

Rust recedes

Question: How can you treat objects that are heavily corroded by rust?

Answer: The first recipe: a mixture of 50 g of lactic acid and 100 ml of vaseline oil. The acid converts iron metahydroxide from rust into an oil-soluble salt, iron lactate. The cleaned surface is wiped with a cloth moistened with vaseline oil.

The second recipe: a solution of 5 g of zinc chloride and 0.5 g of potassium hydrotartrate dissolved in 100 ml of water. Zinc chloride in an aqueous solution undergoes hydrolysis and creates an acidic environment. Iron metahydroxide dissolves due to the formation of soluble iron complexes with tartrate ions in an acidic medium.

Question: How to unscrew a rusted nut with improvised means?

Answer: A rusted nut can be moistened with kerosene, turpentine, or oleic acid. After a while, she manages to turn it off. If the nut "persists", you can set fire to the kerosene or turpentine with which it was moistened. This is usually sufficient to separate the nut and bolt. The most radical way: a very hot soldering iron is applied to the nut. The metal of the nut expands and the rust lags behind the threads; now a few drops of kerosene, turpentine or oleic acid can be poured into the gap between the bolt and the nut. This time, the nut will definitely loosen!

There is another way to separate rusty nuts and bolts. A “cup” of wax or plasticine is made around the rusted nut, the rim of which is 3-4 mm higher than the level of the nut. Dilute sulfuric acid is poured into it and a piece of zinc is placed. After a day, the nut will easily turn off with a wrench. The fact is that a cup with acid and metallic zinc on an iron base is a miniature galvanic cell. The acid dissolves the rust and the iron cations formed are reduced on the zinc surface. And the metal of the nut and bolt does not dissolve in acid as long as it has contact with zinc, since zinc is a more chemically active metal than iron.

Question: What compositions applied on rust are produced by our industry?

Answer: Domestic solvent-borne compositions applied “on rust” include well-known materials: primer (some manufacturers produce it under the name Inkor) and Gremirust primer-enamel. These two-component epoxy paints (base + hardener) contain corrosion inhibitors and targeted additives that allow them to be applied to dense rust up to 100 microns thick. The advantages of these primers are: curing at room temperature, the possibility of applying to a partially corroded surface, high adhesion, good physical and mechanical properties and chemical resistance, ensuring long-term operation of the coating.

Question: What can be used to paint old rusty metal?

Answer: For dense rust, it is possible to use several paints and varnishes containing rust converters:

• primer G-1, primer-paint G-2 (water-borne materials) – at temperatures up to +5°;
• primer-enamel ХВ-0278, primer-enamel AS-0332 – up to minus 5°;
• primer-enamel "ELOKOR SB-022" (materials based on organic solvents) - up to minus 15°С.
• Primer-enamel Tikkurila Coatings, Temabond (tinted according to RAL and TVT)

Question: How to stop the process of metal rusting?

Answer: This can be done with the help of "stainless primer". The primer can be used both as an independent coating on steel, cast iron, aluminum, and in a coating system that includes 1 primer layer and 2 enamel layers. It is also used for priming corroded surfaces.

"Nerjamet-primer" works on the metal surface as a rust converter, chemically binding it, and the resulting polymer film reliably isolates the metal surface from atmospheric moisture. When using the composition, the total cost of repair and restoration work on repainting metal structures is reduced by 3-5 times. The soil is produced ready for use. If necessary, it must be diluted to working viscosity with white spirit. The drug is applied to metal surfaces with remnants of tightly adhering rust and scale with a brush, roller, spray gun. Drying time at +20° - 24 hours.

Question: Roofing often fades. What kind of paint can be used for painting galvanized roofs and gutters?

Answer: Stainless steel cyclone. The coating provides long-term protection against weather, humidity, UV radiation, rain, snow, etc.

Possesses high covering ability and light fastness, does not fade. Significantly extends the service life of galvanized roofs. Also Tikkurila Coatings, Temadur and Temalac coatings.

Question: Can chlorinated rubber paints protect metal from rust?

Answer: These paints are made from chlorinated rubber dispersed in organic solvents. According to their composition, they are volatile resin and have high water and chemical resistance. Therefore, it is possible to use them for corrosion protection of metal and concrete surfaces, water pipes and tanks. Temanil MS-Primer + Temachlor system can be used from Tikkuril Coatings materials.

Anticorrosive in the bath, bathroom, pool

Question: What kind of coating can be used to protect bath containers for cold drinking and hot washing water from corrosion?

Answer: For containers for cold drinking and washing water, KO-42 paint is recommended;, Epovin for hot water - ZincKOS and Teplokor PIGMA compositions.

Question: What are enameled pipes?

Answer: In terms of chemical resistance, they are not inferior to copper, titanium and lead, and at cost are several times cheaper. The use of enameled pipes made of carbon steels instead of stainless steels gives a tenfold cost savings. The advantages of such products include greater mechanical strength, including in comparison with other types of coatings - epoxy, polyethylene, plastic, as well as higher abrasion resistance, which makes it possible to reduce the diameter of pipes without reducing their throughput.

Question: What are the features of re-enamelling bathtubs?

Answer: Enameling can be done with a brush or spray with the participation of professionals, as well as with a brush yourself. Preliminary preparation of the surface of the bath is to remove the old enamel and clean the rust. The whole process takes no more than 4-7 hours, another 48 hours the bath dries, and you can use it after 5-7 days.

Re-enamelling bathtubs require special care. Such baths cannot be washed with powders such as Comet and Pemolux, or using products containing acid, such as Silit. It is unacceptable to get varnishes on the surface of the bath, including for hair, the use of bleach when washing. Such baths are usually cleaned with soaps: washing powders or dishwashing detergents applied to a sponge or soft cloth.

Question: What paintwork materials can be used to re-enamel bathtubs?

Answer: Composition "Svetlana" includes enamel, oxalic acid, hardener, tinting pastes. The bath is washed with water, etched with oxalic acid (stains, stone, dirt, rust are removed and a rough surface is created). Washed with washing powder. Chips close up in advance. Then enamel should be applied within 25-30 minutes. When working with enamel and hardener, contact with water is not allowed. The solvent is acetone. Bath consumption - 0.6 kg; drying - 24 hours. Fully gaining properties after 7 days.

You can also use two-component epoxy-based paint Tikkurila "Reaflex-50". When using glossy bath enamel (white, tinted), either washing powders or laundry soap are used for cleaning. Fully gaining properties after 5 days. Consumption per bath - 0.6 kg. The solvent is industrial alcohol.

B-EP-5297V is used to restore the enamel coating of bathtubs. This paint is glossy, white, tinting is possible. The finish is smooth, even and durable. Do not use abrasive powders of the “Sanitary” type for cleaning. Fully gaining properties after 7 days. Solvents - a mixture of alcohol with acetone; R-4, No. 646.

Question: How to protect against breakage of steel reinforcement in the swimming pool bowl?

Answer: If the condition of the ring drainage of the pool is unsatisfactory, softening and suffusion of the soil is possible. The penetration of water under the bottom of the tank can cause subsidence of the soil and the formation of cracks in concrete structures. In these cases, the reinforcement in the cracks can corrode to breakage.

In such complex cases, the reconstruction of damaged reinforced concrete structures of the reservoir should include the implementation of a protective sacrificial layer of shotcrete on the surfaces of reinforced concrete structures exposed to the leaching action of water.

Obstacles to biodegradation

Question: What external conditions determine the development of wood-destroying fungi?

Answer: The most favorable conditions for the development of wood-destroying fungi are: the presence of air nutrients, sufficient wood moisture and favorable temperature. The absence of any of these conditions will delay the development of the fungus, even if it is firmly established in the wood. Most fungi develop well only at high relative humidity (80-95%). When wood moisture is below 18%, the development of fungi practically does not occur.

Question: What are the main sources of wood moisture and what is their danger?

Answer: The main sources of wood moisture in the structures of various buildings and structures include ground (underground) and surface (storm and seasonal) water. They are especially dangerous for wooden elements of open structures located in the ground (pillars, piles, power transmission line and communication supports, sleepers, etc.). Atmospheric moisture in the form of rain and snow threatens the ground part of open structures, as well as the outer wooden elements of buildings. Operational moisture in a drop-liquid or vapor form in residential premises is present in the form of household moisture released during cooking, washing, drying clothes, washing floors, etc.

A large amount of moisture is introduced into the building when laying raw wood, applying masonry mortars, concreting, etc. For example, 1 sq.m of laid wood with a moisture content of up to 23%, when dried to 10-12%, releases up to 10 liters of water.

The wood of buildings, which dries out naturally, is in danger of decay for a long time. If chemical protection measures were not provided, it, as a rule, is affected by the house fungus to such an extent that the structures become completely unusable.

Condensation moisture that occurs on the surface or in the thickness of structures is dangerous because, as a rule, it is detected already when irreversible changes have occurred in the enclosing wooden structure or its element, for example, internal decay.

Question: Who are the "biological" enemies of the tree?

Answer: These are mold, algae, bacteria, fungi and antimycetes (this is a cross between fungi and algae). Almost all of them can be dealt with with antiseptics. The exception is fungi (saprophytes), since antiseptics act only on some of their species. But it is fungi that are the cause of such widespread rot, which is the most difficult to deal with. Professionals divide rot by color (red, white, gray, yellow, green and brown). Red rot affects coniferous wood, white and yellow - oak and birch, green - oak barrels, as well as wooden beams and cellar ceilings.

Question: Are there ways to neutralize white house fungus?

Answer: White house fungus is the most dangerous enemy of wooden structures. The rate of destruction of wood by white house fungus is such that in 1 month it completely "eats" a four-centimeter oak floor. Previously, in the villages, if the hut was affected by this fungus, it was immediately burned to save all other buildings from infection. After that, the whole world built a new hut for the affected family in another place. Currently, in order to get rid of white house fungus, the affected area is dismantled and burned, and the rest is impregnated with 5% chromic (5% solution of potassium dichromate in 5% sulfuric acid), while it is recommended to cultivate the land on 0.5 m deep.

Question: What are the ways to protect the wood from rotting in the early stages of this process?

Answer: If the process of decay has already begun, it can only be stopped by thorough drying and ventilation of wooden structures. In the early stages, disinfectant solutions, for example, such as the antiseptic compositions "Wood Doctor", can help. They are available in three different versions.

Grade 1 is intended for the prevention of wooden materials immediately after their purchase or immediately after the construction of the house. The composition protects against fungus and woodworm.

Grade 2 is used if fungus, mold or "blue" has already appeared on the walls of the house. This composition destroys existing diseases and protects against their future manifestations.

Grade 3 is the most powerful antiseptic, it completely stops the process of decay. More recently, a special composition (grade 4) has been developed for insect control - “anti-bug”.

SADOLIN Bio Clean is a disinfectant for surfaces contaminated with mold, moss, algae, based on sodium hypochlorite.

DULUX WEATHERSHIELD FUNGICIDAL WASH is a highly effective mold, lichen and rot killer. These compounds are used both indoors and outdoors, but they are effective only in the early stages of rot control. In case of serious damage to wooden structures, rotting can be stopped by special methods, but this is a rather difficult job, usually performed by professionals with the help of restoration chemicals.

Question: What protective impregnations and preservative compositions, presented on the domestic market, prevent biocorrosion?

Answer: Of the Russian antiseptic preparations, it is necessary to mention metacid (100% dry antiseptic) or polysept (25% solution of the same substance). Such conservation compositions as "BIOSEPT", "KSD" and "KSD" have proven themselves well. They protect the wood from damage by mold, fungi, bacteria, and the last two, in addition, make the wood difficult to ignite. Texture coatings "AQUATEX", "SOTEKS" and "BIOX" eliminate the occurrence of fungus, mold and wood blue. They are breathable and have a durability of over 5 years.

A good domestic material for wood protection is GLIMS-LecSil glazing impregnation. This is a ready-to-use aqueous dispersion based on styrene-acrylate latex and reactive silane with modifying additives. At the same time, the composition does not contain organic solvents and plasticizers. Glazing sharply reduces the water absorption of wood, as a result of which it can even be washed, including with soap and water, prevents fire impregnation from washing out, due to antiseptic properties it destroys fungi and mold and prevents their further formation.

Of the imported antiseptic compounds for protecting wood, antiseptics from TIKKURILA have proven themselves well. Pinjasol Color is an antiseptic that forms a continuous water-repellent and weather-resistant finish.

Question: What are insecticides and how are they used?

Answer: To combat beetles and their larvae, poisonous chemicals are used - contact and intestinal insecticides. Fluoride and silicofluoride sodium are allowed by the Ministry of Health and have been used since the beginning of the last century; when using them, safety measures must be observed. To prevent damage to wood by a bug, preventive treatment with fluorosilicic compounds or a 7-10% solution of common salt is used. During historical periods of widespread wooden construction, all wood was processed at the harvesting stage. Aniline dyes were added to the protective solution, which changed the color of the wood. In old houses, to this day, you can find red beams.

The material was prepared by L. RUDNITSKY, A. ZHUKOV, E. ABISHEV

Corrosion in Latin means "corrosion", this easily explains the essence of this concept. From a scientific point of view, corrosion is a process of spontaneous destruction of metals due to chemical and physico-chemical interactions with the environment.

The reason for starting this process is the lack of thermodynamic stability of a particular metal when exposed to substances that are in contact with it.

The main advantage of this method is the possibility of using any synthetic wet cleaners.

Cathodic protection of metal against corrosion

Cathodic protection of metal against corrosion can be attributed to one of the main active methods. The essence of this method is as follows: a negative charge electric current is supplied to the product, polarizing the parts of the elements (affected by corrosion), thereby bringing them closer to. The positive pole of the current source is connected to the anode, which reduces the corrosion of the structure to almost zero. Over time, the anode breaks down, so it needs to be changed regularly.

Cathodic protection can be divided into several options:

• polarization from an external source of electric current;
• contact with a metal that has a more negative electric potential of free corrosion in a particular environment;
• decrease in the rate of cathodic protection.

Polarization from an external source of electric current is used quite often to protect those structures that are in water or in soil. The presented type of corrosion protection is best used for tin, zinc, aluminum, copper, titanium, lead and steel (high chromium, carbon, alloy).

The role of an external current source here is played by cathodic protection stations, consisting of a rectifier, anode ground electrode systems, a current supply to the protected structure, a reference electrode, and an anode cable.

Cathodic corrosion protection can be used both independently and in an additional form. It should be noted that the cathodic protection method also has disadvantages. These include the risk of overprotection, that is, there has been a large shift in the potential of the protected object in the negative direction, which brings with it the destruction of protective coatings, corrosion cracking and hydrogen embrittlement of the metal.

Protective protection of metal against corrosion

Protective corrosion protection is a kind of cathodic protection. When using this type of protection, such a metal is attached to the structure or metal, which has a more negative electrical potential. In the course of this, the process of destruction is observed not of the structure itself, but of the tread. After a certain period, the protector becomes corroded and needs to be replaced with a new one.

Tread protection is most often used in cases where there is a small transient resistance between the protector and the environment.

Protectors differ from each other in terms of protective action radii. They are determined by the maximum possible distance at which it is possible to remove the protector, provided that the protective effect is maintained.

This type of protection is used most often in cases where it is impossible or difficult (expensive) to supply current to a metal structure. Protectors can be used to protect structures in neutral environments, such as sea water, river water, air, soil, and the like.

Protectors are made of the following metals: zinc, aluminum, magnesium, iron. As for pure metals, they are not able to fully fulfill the protective functions assigned to them and therefore require additional alloying in the manufacture of protectors.

Practical methods, as well as a list of tools and products suitable for use when cleaning an acrylic bath, are described.

From all of the above, we can conclude that the modern science of the corrosion of metals, as well as the fight against it, has quite a lot of success. To date, new, increasing volumes of metal products are being introduced into the production of many countries, and as a result, losses are growing every year in the form of millions of tons of corroded metal and huge losses of money that were spent on fighting corrosion. All this suggests that scientific research in this area is extremely relevant and important.