Electrochemical protection protection of metal structures from corrosion is based on the imposition of a negative potential on the protected product. High level It demonstrates effectiveness in cases where metal structures are subject to active electrochemical destruction.

1 The essence of anti-corrosion electrochemical protection

Any metal structure begins to deteriorate over time as a result of corrosion. For this reason, metal surfaces must be mandatory coated with special compounds consisting of various inorganic and organic elements. Such materials reliably protect the metal from oxidation (rusting) for a certain period. But after some time they need to be updated (new compounds applied).

Then, when the protective layer cannot be renewed, corrosion protection of pipelines, car bodies and other structures is carried out using electrochemical techniques. It is indispensable for protecting against rusting tanks and containers operating underground, the bottoms of sea ships, various underground communications, when the corrosion potential (it is called free) is in the zone of repassivation of the base metal of the product or its active dissolution.

The essence of electrochemical protection is that a direct electric current is connected from the outside to a metal structure, which forms cathode-type polarization of microgalvanic couple electrodes on the surface of the metal structure. As a result, the transformation of anodic regions into cathodic ones is observed on the metal surface. After such a transformation, the negative influence of the environment is perceived by the anode, and not the material itself from which the protected product is made.

Electrochemical protection can be either cathodic or anodic. With cathodic potential, the metal potential shifts to the negative side, and with anodic potential, it shifts to positive.

2 Cathodic electrical protection - how does it work?

The mechanism of the process, if you understand it, is quite simple. A metal immersed in an electrolytic solution is a system with a large number of electrons, which includes spatially separated cathode and anode zones, electrically closed to each other. This state of affairs is due to the heterogeneous electrochemical structure of metal products (for example, underground pipelines). Corrosion manifestations form on the anodic areas of the metal due to its ionization.

When a material with a high potential (negative) is added to the base metal located in the electrolyte, the formation of a common cathode is observed due to the process of polarization of the cathode and anodic zones. By high potential we mean a value that exceeds the potential of the anodic reaction. In the formed galvanic couple, a material with a low electrode potential dissolves, which leads to the suspension of corrosion (since the ions of the protected metal product cannot enter the solution).

The electric current required to protect the car body, underground tanks and pipelines, and the bottoms of ships can come from an external source, and not just from the functioning of a microgalvanic couple. In such a situation, the protected structure is connected to the “minus” of the electric current source. The anode, made of materials with a low degree of solubility, is connected to the “plus” of the system.

If the current is obtained only from galvanic couples, we speak of a process with sacrificial anodes. And when using current from an external source, we are talking about protecting pipelines, parts of vehicles and water vehicles with the help of superimposed current. The use of any of these schemes provides high-quality protection of the object from general corrosive decay and from a number of its special variants (selective, pitting, cracking, intergranular, contact types of corrosion).

3 How does the anodic technique work?

This electrochemical technique for protecting metals from corrosion is used for structures made of:

• carbon steels;
• passivating dissimilar materials;
• highly alloyed and;
• titanium alloys.

The anode scheme involves shifting the potential of the protected steel in a positive direction. Moreover, this process continues until the system enters a stable passive state. Such corrosion protection is possible in environments that are good conductors of electrical current. The advantage of the anodic technique is that it significantly slows down the rate of oxidation of the protected surfaces.

In addition, such protection can be carried out by saturating the corrosive environment with special oxidizing components (nitrates, dichromates and others). In this case, its mechanism is approximately identical to the traditional method of anodic polarization of metals. Oxidizing agents significantly increase the effect of the cathodic process on the steel surface, but they usually have a negative effect on environment, throwing aggressive elements into it.

Anodic protection is used less frequently than cathodic protection, since many specific requirements are put forward for the protected object (for example, impeccable quality of welds of pipelines or a car body, constant presence of electrodes in the solution, etc.). In anode technology, cathodes are placed according to a strictly defined scheme, which takes into account all the features of the metal structure.

For the anodic technique, poorly soluble elements are used (cathodes are made from them) - platinum, nickel, stainless high-alloy alloys, lead, tantalum. The installation itself for such corrosion protection consists of the following components:

• protected structure;
• current source;
• cathode;
• special reference electrode.

It is allowed to use anodic protection for containers where mineral fertilizers, ammonia compounds, sulfuric acid are stored, for cylindrical installations and heat exchangers operated at chemical plants, for tanks in which chemical nickel plating is performed.

4 Features of tread protection for steel and metal

A fairly frequently used option for cathodic protection is the technology of using special protector materials. With this technique, an electronegative metal is connected to the structure. Over a given period of time, corrosion affects the protector, and not the protected object. After the protector is destroyed to a certain level, a new “defender” is installed in its place.

Protective electrochemical protection is recommended for treating objects located in soil, air, water (that is, in chemically neutral environments). Moreover, it will be effective only when there is some transition resistance between the medium and the protector material (its value varies, but in any case it is small).

In practice, protectors are used when it is economically infeasible or physically impossible to supply the required charge of electric current to an object made of steel or metal. It is worth separately noting the fact that protective materials are characterized by a certain radius over which their positive effect extends. For this reason, you should correctly calculate the distance to remove them from the metal structure.

Popular protectors:

• Magnesium. They are used in environments with a pH of 9.5–10.5 units (soil, fresh and slightly salted water). They are made from magnesium-based alloys with additional alloying with aluminum (no more than 6–7%) and zinc (up to 5%). For the environment, such protectors that protect objects from corrosion are potentially unsafe due to the fact that they can cause cracking and hydrogen embrittlement of metal products.
• Zinc. These “protectors” are indispensable for structures operating in water with a high salt content. There is no point in using them in other environments, since hydroxides and oxides appear on their surface in the form of a thick film. Zinc-based protectors contain minor (up to 0.5%) additives of iron, lead, cadmium, aluminum and some other chemical elements.
• Aluminum. They are used in sea running water and at objects located on the coastal shelf. Aluminum protectors contain magnesium (about 5%) and zinc (about 8%), as well as very small amounts of thallium, cadmium, silicon, and indium.

In addition, iron protectors are sometimes used, which are made from iron without any additives or from ordinary carbon steels.

5 How is the cathode circuit performed?

Temperature changes and ultraviolet rays cause serious damage to all external components and components Vehicle. Protecting the car body and some of its other elements from corrosion by electrochemical methods is recognized as a very effective way to prolong the ideal appearance of the car.

The principle of operation of such protection is no different from the scheme described above. When protecting a car body from rusting, the function of an anode can be performed by almost any surface that is capable of efficiently conducting electric current (wet road surfaces, metal plates, steel structures). The cathode in this case is the housing itself. vehicle.

Elementary methods of electrochemical protection of a car body:

1. We connect the body of the garage in which the car is parked through the mounting wire and an additional resistor to the battery positive. This protection against corrosion of the car body is especially effective in the summer, when the greenhouse effect is present in the garage. This effect precisely protects the external parts of the car from oxidation.
2. We install a special grounding metalized rubber “tail” in the rear of the vehicle so that drops of moisture fall on it while driving in rainy weather. At high humidity, a potential difference is formed between the highway and the car body, which protects the outer parts of the vehicle from oxidation.

The car body is also protected using protectors. They are mounted on the thresholds of the car, on the bottom, under the wings. The protectors in this case are small plates made of platinum, magnetite, carboxyl, graphite (anodes that do not deteriorate over time), as well as aluminum and “stainless steel” (they should be replaced every few years).

6 Nuances of anti-corrosion protection of pipelines

Pipe systems are currently protected using drainage and cathodic electrochemical techniques. When protecting pipelines from corrosion using the cathodic scheme, the following are used:

• External current sources. Their plus will be connected to the anode grounding, and the minus to the pipe itself.
• Protective anodes using current from galvanic pairs.

The cathodic technique involves the polarization of the protected steel surface. In this case, underground pipelines are connected to the “minus” of the cathodic protection complex (in fact, it is a current source). “Plus” is connected to the additional external electrode using a special cable, which is made of conductive rubber or graphite. This circuit allows you to obtain a closed-type electrical circuit, which includes the following components:

• electrode (external);
• electrolyte located in the soil where the pipelines are laid;
• pipes directly;
• cable (cathode);
• current source;
• cable (anode).

For tread protection of pipelines, materials based on aluminum, magnesium and zinc are used, the efficiency of which is 90% when using protectors based on aluminum and zinc and 50% for protectors made of magnesium alloys and pure magnesium.

For drainage protection of pipe systems, technology is used to drain stray currents into the ground. There are four options for drainage piping - polarized, earthen, reinforced and straight. With direct and polarized drainage, jumpers are placed between the “minus” of stray currents and the pipe. For the earth protection circuit, it is necessary to make grounding using additional electrodes. And with increased drainage of pipe systems, a converter is added to the circuit, which is necessary to increase the magnitude of the drainage current.

INTERSTATE STANDARD

Unified system of protection against corrosion and aging

METALS AND ALLOYS

Determination methods
corrosion indicators
and corrosion resistance

GOST 9.908-85

MOSCOW
IPC PUBLISHING HOUSE OF STANDARDS
1999

INTERSTATE STANDARD

Date of introduction 01.01.87

This standard establishes the main indicators of corrosion and corrosion resistance (chemical resistance) of metals and alloys for continuous, pitting, intergranular, exfoliating corrosion, spot corrosion, stress-corrosion cracking, corrosion fatigue and methods for their determination. Indicators of corrosion and corrosion resistance are used in corrosion research, testing, inspection of equipment and defect detection of products during production, operation, and storage.

1. INDICATORS OF CORROSION AND CORROSION RESISTANCE

Diagram of the dependence of the corrosion effect (integral indicator) at from time

1.6. It is allowed to use, along with the indicators given in the table, other quantitative indicators determined by operational requirements, the high sensitivity of experimental methods or the possibility of using them for remote monitoring of the corrosion process, with a preliminary establishment of the relationship between the main and applied indicators. As such indicators of corrosion, taking into account its type and mechanism, the following can be used: the amount of hydrogen released and (or) absorbed by the metal, the amount of reduced (absorbed) oxygen, an increase in the mass of the sample (while maintaining solid corrosion products on it), a change in the concentration of corrosion products in environment (with their complete or partial solubility), an increase in electrical resistance, a decrease in reflectivity, heat transfer coefficient, a change in acoustic emission, internal friction, etc. For electrochemical corrosion, the use of electrochemical indicators of corrosion and corrosion resistance is allowed. For crevice and contact corrosion, corrosion and corrosion resistance indicators are selected from the table in accordance with the type of corrosion (solid or pitting) in the crevice (gap) or contact area. 1.7. For one type of corrosion, it is possible to characterize the results of corrosion tests using several corrosion indicators. If there are two or more types of corrosion on one sample (product), each type of corrosion is characterized by its own indicators. Corrosion resistance in this case is assessed by an indicator that determines the performance of the system. 1.8. If it is impossible or impractical to determine quantitative indicators of corrosion resistance, it is allowed to use qualitative indicators, for example, changes in the appearance of the metal surface. In this case, the presence of tarnish is visually determined; corrosion damage, the presence and nature of the layer of corrosion products; the presence or absence of an undesirable change in the environment, etc. Based on the qualitative indicator of corrosion resistance, an assessment is made of the type: resistant - not resistant; pass - fail, etc. Changes in appearance can be assessed using conventional scales, for example, for electronic products according to GOST 27597. 1.9. Acceptable indicators of corrosion and corrosion resistance are established in the regulatory and technical documentation for the material, product, equipment.

2. DETERMINATION OF CORROSION INDICATORS

Where m 0 - mass of the sample before testing, kg; m 1 - mass of the sample after testing and removal of corrosion products, kg; S- surface area of ​​the sample, m2. 2.1.2. When hard-to-remove solid corrosion products are formed or their removal is impractical, a quantitative assessment of continuous corrosion is carried out by increasing mass. The increase in mass per unit surface area is calculated from the difference in mass of the sample before and after testing, per unit surface area of ​​the sample. To calculate the loss of metal mass from an increase in the mass of the sample, it is necessary to know the composition of the corrosion products. This indicator of metal corrosion in gases at high temperatures is determined according to GOST 6130. 2.1.3. Corrosion products are removed according to GOST 9.907. 2.1.4. The change in dimensions is determined by direct measurements of the difference between the dimensions of the sample before and after testing and removal of corrosion products. If necessary, change the dimensions according to mass loss taking into account the geometry of the sample, for example, change the thickness of a flat sample D L, m, is calculated using the formula

Where D m- mass loss per unit area, kg/m2; ρ - metal density, kg/m3. 2.2. Spot corrosion 2.2.1. The area of ​​each spot is determined with a planimeter. If such a measurement is not possible, the spot is outlined with a rectangle and its area is calculated. 2.2.2. The degree of damage to the metal surface by corrosion stains ( G) as a percentage is calculated using the formula

Where S i- square i-that spot, m 2; n - number of spots; S - surface area of ​​the sample, m2. In case of spot corrosion, it is allowed to determine the degree of surface damage by corrosion using a grid of squares. 2.3. Pitting corrosion 2.3.1. The maximum depth of penetration of pitting corrosion is determined by: measuring with a mechanical indicator with a movable needle probe the distance between the mouth plane and the bottom of the pit after removing corrosion products in cases where the dimensions of the pit allow free penetration of the needle probe to its bottom; microscopically, after removing corrosion products by measuring the distance between the mouth plane and the bottom of the pitting (double focusing method); microscopically on a transverse section with appropriate magnification; sequential mechanical removal of metal layers of a given thickness, for example, 0.01 mm at a time until the last pitting disappears. Pittings with an opening diameter of at least 10 µm are taken into account. The total working surface area must be at least 0.005 m2. 2.3.2. A thin section to measure the maximum depth of penetration of pitting corrosion is cut out from the area where the largest pittings are located on the working surface. The cutting line should pass through as many of these pittings as possible. 2.3.3. The maximum depth of penetration of pitting corrosion is found as the arithmetic mean of measurements of the deepest pittings depending on their number ( n) on the surface: at n < 10 измеряют 1-2 питтинга, при n < 20 - 3-4, при n> 20 - 5. 2.3.4. For penetrating pitting corrosion, the thickness of the sample is taken as the maximum penetration depth. 2.3.5. The maximum diameter of the pitting is determined using measuring instruments or optical means. 2.3.6. The degree of damage to a metal surface by pitting is expressed as the percentage of the surface area occupied by pitting. If there are a large number of pittings with a diameter of more than 1 mm, it is recommended to determine the degree of damage according to clause 2.2. 2.4. Intergranular corrosion 2.4.1. The depth of intergranular corrosion is determined by the metallographic method according to GOST 1778 on an etched section made in the transverse plane of the sample, at a distance from the edges of at least 5 mm with a magnification of 50 ´ or more. It is allowed to determine the penetration depth of corrosion of aluminum and aluminum alloys using unetched sections. The etching mode is in accordance with GOST 6032, GOST 9.021 and NTD. (Changed edition, Amendment No. 1). 2.4.2. Changes in mechanical properties during intergranular corrosion - tensile strength, relative elongation, impact strength - are determined by comparing the properties of metal samples that were and were not subject to corrosion. The mechanical properties of metal samples that have not been subjected to corrosion are taken as 100%. 2.4.3. Samples are prepared according to GOST 1497 and GOST 11701 when determining tensile strength and relative elongation, and according to GOST 9454 when determining impact strength. 2.4.4. It is allowed to use physical methods to control the depth of corrosion penetration in accordance with GOST 6032. 2.5. Stress-corrosion cracking and corrosion fatigue 2.5.1. In case of corrosion cracking and corrosion fatigue, cracks are detected visually or using optical or other flaw detection means. It is possible to use indirect measurement methods, for example, determining the increase in the electrical resistance of the sample. 2.5.2. The change in mechanical properties is determined according to clause 2.4.2. 2.6. Exfoliation corrosion 2.6.1. The degree of surface damage during exfoliating corrosion is expressed as a percentage of the area with peeling on each surface of the sample according to GOST 9.904. 2.6.2. The total length of the ends with cracks for each sample ( L) as a percentage is calculated using the formula

Where L i- length of the end section affected by cracks, m; P- sample perimeter, m. 2.6.3. It is allowed to use a conditional scale score according to GOST 9.904 as a generalized semi-quantitative (score) indicator of exfoliation corrosion.

3. DETERMINATION OF CORROSION RESISTANCE INDICATORS

Where tm- time until the mass per unit area decreases by the permissible value D m, year; v m- rate of mass loss, kg/m 2 ∙year; t 1 - time of penetration to the permissible (specified) depth ( l), year; v 1 - linear corrosion rate, m/year. 3.1.3. When continuous corrosion occurs at an unstable rate, corrosion resistance indicators are determined according to clause 1.5. 3.1.4. If there are special requirements for the optical, electrical and other properties of the metal, its corrosion resistance is assessed by the time it takes for these properties to change to an acceptable (specified) level. 3.2. Spot corrosion An indicator of corrosion resistance for spot corrosion is time (t n) achieving an acceptable degree of surface damage. t value n determined graphically according to clause 1.5. 3.3. Pitting corrosion 3.3.1. The main indicator of corrosion resistance against pitting corrosion is the absence of pitting or the minimum time (t pit) for pitting to penetrate to the permissible (specified) depth. t pit is determined graphically from the dependence of the maximum pitting depth l max from time. 3.3.2. An indicator of resistance to pitting corrosion can also be the time it takes to reach the permissible degree of damage to the surface by pitting. 3.4. Intergranular corrosion 3.4.1. Indicators of corrosion resistance against intergranular corrosion are generally determined graphically or analytically from the time dependence of the penetration depth or mechanical properties in accordance with clause 1.5. 3.4.2. A qualitative assessment of resistance to intergranular corrosion of the type of struts - not struts based on accelerated tests of corrosion-resistant alloys and steel is established according to GOST 6032, aluminum alloys - according to GOST 9.021. 3.5. Corrosion cracking 3.5.1. Quantitative indicators of resistance to corrosion cracking are determined for high-strength steels and alloys according to GOST 9.903, for aluminum and magnesium alloys - according to GOST 9.019, welded joints of steel, copper and titanium alloys - according to GOST 26294-84. 3.6. Exfoliation corrosion 3.6.1. Indicators of resistance to exfoliation corrosion for aluminum and its alloys are determined according to GOST 9.904, for other materials - according to NTD.

4. PROCESSING RESULTS

ANNEX 1

Mandatory

METALLOGRAPHIC METHOD FOR ASSESSING CORROSION DAMAGES

1. Essence of the method

The method is based on determining the type of corrosion, the form of corrosion damage, the distribution of corrosion damage in metals, alloys and protective metal coatings (hereinafter referred to as materials) by comparison with the corresponding standard forms, as well as measuring the depth of corrosion damage on a metallographic section.

2. Samples

2.1. The location for taking samples from the test material is selected based on the results of a visual (with the naked eye or using a magnifying glass) inspection of the surface or non-destructive flaw detection. 2.2. Samples are cut from the following places of the material: 1) if only part of the surface of the material is affected by corrosion, samples are taken in three places: from the part affected by corrosion; from the part not affected by corrosion and in the area between them; 2) if there are areas of the surface of the material with different types of corrosion or with different depths of corrosion damage, samples are taken from all areas affected by corrosion; 3) if there is one type of corrosion damage on the surface of the material, samples are taken from at least three characteristic areas of the material under study. 2.3. If necessary, at least one sample is taken from at least five functionally necessary areas of the test material. The sample size is determined based on the size of the corrosion zone. 2.4. The samples are cut so that the plane of the section is perpendicular to the surface under study. The manufacturing method should not affect the structure of the material and destroy the surface layer and edges of the sample. For materials with protective coatings, damage to the coating and its separation from the base material is not allowed. 2.5. Sample marking - according to GOST 9.905. 2.6. When making a metallographic section, all traces of cutting, for example, burrs, are removed from the surface of the sample. 2.7. During grinding and polishing operations, it is necessary to ensure that the nature and size of the corrosion damage does not change. The edges of the polished section at the site of corrosion damage should not be rounded. Roundings are allowed that do not affect the accuracy of determining corrosion damage. To do this, it is recommended to pour the sample into the casting compound in such a way that the edge being examined is at a distance of at least 10 mm from the edge of the section. Polishing is carried out briefly using diamond pastes. 2.8. The section is assessed before and after etching. Etching makes it possible to distinguish between corrosion damage and the structure of the material. When etching, the nature and size of the corrosion lesion should not be changed.

3. Carrying out the test

3.1. Determination and assessment of the type of corrosion, the form of corrosion damage and its distribution in the material 3.1.1. When conducting the test, it is necessary to take into account the chemical composition of the material being tested, the method of its processing, as well as all corrosive factors. 3.1.2. The test is carried out on a metallographic section under a microscope at a magnification of 50, 100, 500 and 1000´. 3.1.3. When determining the type of corrosion, corrosion control is carried out along the entire length of the section. It is possible to determine several types of corrosion on one sample. 3.1.4. When testing protective coatings, the type of corrosion of the coating and the base material is determined separately. 3.1.5. If the material, in addition to the corrosive environment, is affected by other factors that influence the change in the structure of the material, for example, high temperature, mechanical stress, corrosion damage is determined by comparing the material with a specific sample exposed to similar factors, but protected from the effects of a corrosive environment. 3.1.6. Assessment of the form of corrosion damage and determination of the type of corrosion is carried out by comparison with typical schemes of corrosion damage according to Appendix 2, distribution of corrosion damage in the material - according to Appendix 3. 3.2. Measuring the depth of corrosion damage 3.2.1. The depth of corrosion damage is determined on a micrometallographic section using an ocular scale and a micrometer screw of a microscope. 3.2.2. The depth of corrosion damage is determined by the difference in the thickness of the metal of the corroded section of the surface of the polished section and the surface area without corrosion or by measuring the depth of damage from a surface that is not damaged or slightly damaged by corrosion. When testing a material with a protective coating, the results of measuring the depth of corrosion damage to the coating and the base metal are determined separately. 3.2.3. If the entire surface of the sample is affected by corrosion and the depth of corrosion damage in different areas of the surface does not differ noticeably, for example in the case of intergranular or transgranular corrosion, the depth of corrosion damage is measured in at least 10 areas of the surface. For large samples, measurements are taken in at least 10 areas for every 20 mm of the length of the controlled surface, taking into account the deepest lesions. 3.2.4. In case of local corrosion damage (for example, pitting corrosion or stain corrosion), measurements are carried out in the places of this corrosion damage, and the number of areas for measurements may differ from the requirements given in paragraph. 3.2.3. 3.2.5. To clarify the determination of the maximum depth of corrosion damage, after a metallographic assessment of the sections, they are re-polished: 1) for samples with local corrosion damage, for example, stain corrosion or pitting corrosion - to the maximum depth of corrosion damage, i.e. until the moment when the measured depth is less than the previous measurement result; 2) for samples with almost the same depth of corrosion damage in different areas of the surface, after evaluation, they are re-polished and a new metallographic section is made, on which the corrosion damage is again assessed. 3.2.6. The error in measuring the depth of corrosion damage is no more than ±10%.

4. Test report - according to GOST 9.905

APPENDIX 2

Mandatory

TYPES OF CORROSION

APPENDIX 3

Mandatory

DISTRIBUTION OF CORROSION

INFORMATION DATA

To protect metals from corrosion, various methods are used, which can be divided into the following main areas: alloying of metals; protective coatings (metallic, non-metallic); electrochemical protection; changes in the properties of the corrosive environment; rational product design.

Alloying of metals. This effective method increasing the corrosion resistance of metals. When alloying, alloying elements (chromium, nickel, molybdenum, etc.) are introduced into the composition of an alloy or metal, causing the passivity of the metal. Passivation is the process of transition of a metal or alloy to a state of increased corrosion resistance caused by inhibition of the anodic process. The passive state of the metal is explained by the formation on its surface of a structurally perfect oxide film (the oxide film has protective properties provided that the crystal lattices of the metal and the resulting oxide are as similar as possible).

Alloying has found wide application for protection against gas corrosion. Iron, aluminum, copper, magnesium, zinc, as well as alloys based on them, are subject to alloying. The result is alloys with higher corrosion resistance than the metals themselves. These alloys simultaneously have heat resistance And heat resistance.

Heat resistance– resistance to gas corrosion at high temperatures. Heat resistance– properties of a structural material to maintain high mechanical strength at a significant increase in temperature. Heat resistance is usually achieved by alloying metals and alloys, such as steel with chromium, aluminum and silicon. At high temperatures, these elements oxidize more energetically than iron, and thus form dense protective films of oxides, for example Al 2 O 3 and Cr 2 O 3.

Alloying is also used to reduce the rate of galvanic corrosion, especially hydrogen evolution corrosion. Corrosion-resistant alloys, for example, include stainless steels in which chromium, nickel and other metals are alloying components.

Protective coatings. Layers artificially created on the surface of metal products to protect them from corrosion are called protective coatings. Application of protective coatings is the most common method of combating corrosion. Protective coatings not only protect products from corrosion, but also give surfaces a number of valuable physical and chemical properties (wear resistance, electrical conductivity, etc.). They are divided into metallic and non-metallic. The general requirements for all types of protective coatings are high adhesive ability, continuity and durability in an aggressive environment.

Metal coatings. Metal coatings occupy a special position, since their action is dual. As long as the integrity of the coating layer is not compromised, its protective effect is reduced to isolating the surface of the protected metal from the environment. This is no different from the effect of any mechanical protective layer (painting, oxide film, etc.). Metal coatings must be impervious to corrosive agents.

When the coating is damaged (or has pores), a galvanic cell is formed. The nature of corrosion destruction of the base metal is determined by the electrochemical characteristics of both metals. Protective anti-corrosion coatings can be cathode And anodic. TO cathode coatings These include coatings whose potentials in a given environment have a more positive value than the potential of the base metal. Anodic coatings have a more negative potential than the potential of the base metal.

So, for example, in relation to iron, the nickel coating is cathodic, and the zinc coating is anodic (Fig. 2).

When the nickel coating is damaged (Fig. 2, a) in the anodic areas, the process of iron oxidation occurs due to the appearance of microcorrosive galvanic elements. At the cathode sections - hydrogen reduction. Consequently, cathodic coatings can protect metal from corrosion only in the absence of pores and damage to the coating.

Local damage to the protective zinc layer leads to its further destruction, while the surface of the iron is protected from corrosion. The zinc oxidation process occurs at the anodic sites. At the cathode sections - hydrogen reduction (Fig. 2,b).

The electrode 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.

Various methods are used to obtain metal protective coatings: electrochemical(electroplating); immersion in molten metal(hot-dip galvanizing, tinning); metallization(applying molten metal to the protected surface using a jet of compressed air); chemical(obtaining metal coatings using reducing agents, such as hydrazine).

Rice. 2. Corrosion of iron in an acid solution with cathodic (a) and anodic (b) coatings: 1 – base metal; 2 – coating; 3 – electrolyte solution.

Materials for metal protective coatings can be either pure metals (zinc, cadmium, aluminum, nickel, copper, chromium, silver, etc.) or their alloys (bronze, brass, etc.).

Non-metallic protective coatings. They can be either inorganic or organic. The protective effect of these coatings is mainly reduced to isolating the metal from the environment.

Inorganic coatings include inorganic enamels, metal oxides, compounds of chromium, phosphorus, etc. Organic coatings include paint coatings, coatings with resins, plastics, polymer films, and rubber.

Inorganic enamels are silicates in their composition, i.e. silicon compounds. The main disadvantages of such coatings include brittleness and cracking due to thermal and mechanical shocks.

Paint and varnish coatings most common. The paint and varnish coating must be continuous, gas- and waterproof, chemically resistant, elastic, have high adhesion to the material, mechanical strength and hardness.

Chemical methods very diverse. These include, for example, treating the surface of a metal with substances that enter into a chemical reaction with it and form a film of a stable chemical compound on its surface, in the formation of which the protected metal itself takes part. Such methods include oxidation, phosphating, sulfidation and etc.

Oxidation- the process of formation of oxide films on the surface of metal products.

The modern method of oxidation is chemical and electrochemical processing of parts in alkaline solutions.

For iron and its alloys, alkaline oxidation is most often used in a solution containing NaOH, NaNO 3, NaNO 2 at a temperature of 135-140 ° C. Oxidation of ferrous metals is called bluing.

Fe
Fe 2+ + 2

The reduction process occurs at the cathode sections:

2 H 2 O + O 2 + 4
4OH -

On the surface of the metal, as a result of the work of microgalvanic cells, Fe(OH) 2 is formed, which is then oxidized into Fe 3 O 4. The oxide film on low-carbon steel is deep black, and on high-carbon steel it is black with a grayish tint.

Fe 2+ + 2OH -
Fe(OH) 2 ;

12 Fe(OH) 2 + NaNO 3
4Fe 3 O 4 + NaOH + 10 H 2 O + NH 3

The anti-corrosion properties of the surface film of oxides are low, so the scope of application of this method is limited. The main purpose is decorative finishing. Blueing is used when it is necessary to maintain the original dimensions, since the oxide film is only 1.0 - 1.5 microns.

Phosphating- a method for producing phosphate films on products made of non-ferrous and ferrous metals. For phosphating, a metal product is immersed in solutions of phosphoric acid and its acid salts (H 3 PO 4 + Mn(H 2 PO 4) 2) at a temperature of 96-98 o C.

On the surface of the metal, as a result of the operation of microgalvanic cells, a phosphate film is formed, which has a complex chemical composition and contains poorly soluble hydrates of two- and three-substituted manganese and iron phosphates: MnHPO 4, Mn 3 (PO 4) 2, FeHPO 4, Fe 3 (PO 4 ) 2  n H2O.

The oxidation process occurs at the anodic sites:

Fe
Fe 2+ + 2

At the cathode sections, the process of hydrogen reduction occurs:

2H + + 2
H 2 (pH< 7)

When Fe 2+ ions interact with the anions of orthophosphoric acid and its acid salts, phosphate films are formed:

Fe 2+ + H 2 PO - 4
FeHPO4+H+

3Fe 2+ + 2 PO 4 3-
Fe 3 (PO 4) 2

The resulting phosphate film is chemically bonded to the metal and consists of intergrown crystals separated by ultramicroscopic pores. Phosphate films have good adhesion and have a developed rough surface. They are a good primer for applying paints and penetrating lubricants. Phosphate coatings are used mainly to protect metals from corrosion in enclosed spaces, and also as a method of preparing the surface for subsequent painting or varnishing. The disadvantage of phosphate films is low strength and elasticity, high fragility.

Anodizing- This is the process of formation of oxide films on the surface of metal and especially aluminum. Under normal conditions, a thin oxide film of Al 2 O 3 or Al 2 O 3 ∙ nH 2 O oxides is present on the surface of aluminum, which cannot protect it from corrosion. Under the influence of the environment, aluminum becomes covered with a layer of corrosion products. The process of artificial formation of oxide films can be carried out by chemical and electrochemical methods. In the electrochemical oxidation of aluminum, the aluminum product plays the role of the anode of the electrolyzer. The electrolyte is a solution of sulfuric, orthophosphoric, chromic, boric or oxalic acids; the cathode can be a metal that does not interact with the electrolyte solution, for example stainless steel. Hydrogen is released at the cathode, and aluminum oxide is formed at the anode. The overall process at the anode can be represented by the following equation:

2 Al + 3 H 2 O
Al 2 O 3 + 6 H + + 6

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

The second group of methods allows, if necessary, to create new protection modes that ensure the least corrosion of the product. For example, in certain sections of the pipeline, depending on the aggressiveness of the soil, the cathode current density can be changed. Or use different inhibitors for different types of oil pumped through pipes.

Question: How are corrosion inhibitors used?

Answer: To combat metal corrosion, corrosion inhibitors are widely used, which are introduced in small quantities into an aggressive environment and create an adsorption film on the metal surface, inhibiting electrode processes and changing 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 pigments and the film-forming base, paint and varnish coatings can serve as a barrier, passivator or protector.

Barrier protection is the mechanical insulation 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 environment to the base and the occurrence of under-film corrosion.

Passivation of a metal surface using paintwork is achieved through chemical interaction between the metal and the 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.

Protective protection of metal is achieved by adding powdered metals to the coating material, creating donor electron pairs with the protected metal. For steel these are zinc, magnesium, aluminum. Under the influence of an aggressive environment, the additive powder gradually dissolves, and the base material is not subject to corrosion.

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

Answer: Firstly, the durability of metal protection against corrosion depends on the type (and kind) of the used paint coating. Secondly, the thoroughness of preparing the metal surface for painting plays a decisive role. The most labor-intensive process in this case is the removal of previously formed corrosion products. Special compounds are applied that destroy rust, followed by mechanical removal with metal brushes.

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

Question: What are high-fill 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%). The market for materials for home use mainly offers single-component materials. The main advantage of highly filled systems compared to conventional ones is significantly better corrosion resistance at a comparable layer thickness, lower material consumption and the possibility of applying a thicker layer, which ensures the required anti-corrosion protection in just 1-2 times.

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

Answer: Anti-corrosion primer based on modified vinyl acrylic resins in the Galvaplast solvent is used for interior and exterior work on descaled ferrous metal substrates, galvanized steel, and galvanized iron. Solvent – ​​white spirit. Application – brush, roller, spray. Consumption 0.10-0.12 kg/sq.m; drying 24 hours.

Question: 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. Sometimes patina refers to oxides on the surface of metals, as well as films that cause tarnish on the surface of stones, marble or wooden objects over time.

The appearance of 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 forms on the surface of copper within 5-25 years, depending on 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 with 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 sulfate. 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 aggressive environments - 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 is provided by: enamels XC-759, “ELOCOR SB-022” varnish, FLC-2, primers, XC-010, etc. In each individual case, a specific painting scheme is selected, according to operating conditions. Tikkurilla Coatings Temabond, Temacoat and Temachlor paints.

Question: What compositions can be used when 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-based hardener. Application - brush, spray. Drying 7 hours.

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

Suitable for use with BEP-0261 primer and BEP-610 enamel.

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

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

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

Question: What compositions should be used to coat 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. Used for painting bridges, tanks, steel structures and equipment. Application - brush, spray. Drying – 6 hours.

Temaline BL is a two-component epoxy coating that does not contain solvents. Used for painting steel surfaces exposed to wear, chemical and mechanical stress when immersed in water, containers for oil or gasoline, tanks and reservoirs, treatment facilities for wastewater. Application by airless spray.

Temazinc is a one-component zinc-rich epoxy paint with a polyamide-based 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 influences. Suitable for painting bridges, cranes, steel frames, steel structures and equipment. Drying 1 hour.

Question: How to protect underground pipes from the formation of fistulas?

Answer: There can be two reasons for any pipe burst: mechanical damage or corrosion. If the first reason is the result of accident and carelessness - the pipe is caught in something or the weld has come apart, then corrosion cannot be avoided; this is a natural phenomenon caused by soil moisture.

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

Question: How much does cathodic polarization cost?

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

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 enough to simply treat with an ammonia solution to remove grease stains and zinc corrosion products from the surface.

Question: How to restore 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 protected using ZNC (zinc-filled compositions)?

Answer: Cold galvanizing technology using CNC guarantees absolute non-toxicity, fire safety, and heat resistance up to +800°C. Coating of metal with this composition is carried out by spraying, with a roller or even just with a brush and provides the product with, in fact, double protection: both cathodic and film. The validity period 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 application on a construction site.
3. No restrictions on overall dimensions protected structures.

Question: At what temperature is thermal diffusion coating applied?

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

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

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

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

Answer: For this, you can use both water-based ones - G-3 primer, G-4 paint, and organo-thinned ones - EP-140, "ELOCOR SB-022", etc. Tikkurila Coatings protective systems can be used: 1 Temakout GPLS-Primer + Temadur, 2 Temaprime EE+Temalak, Temalak and Temadur are tinted according to RAL and TVT.

Question: What paint can be used to paint galvanized drainage pipes?

Answer: Sockelfarg – latex paint in black and white water based. Designed for application to both new and previously painted outdoor surfaces. Resistant to weather conditions. Solvent – ​​water. Drying 3 hours.

Question: Why are water-based anti-corrosion agents rarely used?

Answer: There are 2 main reasons: the increased price compared to conventional materials and the prevailing opinion in certain circles that water systems have worse protective properties. However, as environmental legislation becomes stricter, both in Europe and throughout the world, the popularity of water systems is growing. Experts who tested high-quality water-based materials were able to verify that their protective properties are no 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 “Constant MK” device is the easiest to use - it measures the thickness of 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.

The rust is receding

Question: How can I treat items that are heavily corroded by rust?

Answer: First recipe: a mixture of 50 g of lactic acid and 100 ml of vaseline oil. The acid converts iron metahydroxide from rust into a salt soluble in petroleum jelly - iron lactate. Wipe the cleaned surface with a cloth moistened with petroleum jelly.

Second recipe: a solution of 5 g of zinc chloride and 0.5 g of potassium hydrogen tartrate, dissolved in 100 ml of water. Zinc chloride in 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 environment.

Question: How to unscrew a rusty nut using improvised means?

Answer: A rusted nut can be moistened with kerosene, turpentine or oleic acid. After some time it is possible to unscrew it. If the nut “persists,” you can set fire to the kerosene or turpentine with which it was moistened. This is usually enough to separate the nut and bolt. The most radical method: apply a very heated soldering iron to the nut. The metal of the nut expands and the rust moves away from the thread; Now you can pour a few drops of kerosene, turpentine or oleic acid into the gap between the bolt and the nut. This time the nut will definitely come loose!

There is another way to remove rusty nuts and bolts. A “cup” of wax or plasticine is made around the rusted nut, the edge 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 can be easily unscrewed with a wrench. The fact is that a cup with acid and zinc metal on an iron base is a miniature galvanic cell. The acid dissolves the rust, and the resulting iron cations are reduced to the surface of the zinc. And the metal of the nut and bolt will not dissolve in the acid as long as it is in contact with zinc, since zinc is a more reactive metal than iron.

Question: What anti-rust compounds does our industry produce?

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

Question: How can you paint old rusty metal?

Answer: For stubborn 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 XB-0278, primer-enamel AS-0332 – up to minus 5°;
• primer-enamel “ELOCOR SB-022” (materials based on organic solvents) – up to minus 15°C.
• Primer enamel Tikkurila Coatings, Temabond (tinted according to RAL and TVT)

Question: How to stop the rusting process of metal?

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

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

Question: Roofing often fades. What paint can be used on galvanized roofs and gutters?

Answer: Stainless steel-cycron. The coating provides long-term protection from weather conditions, humidity, ultraviolet radiation, rain, snow, etc.

It has high hiding power and light fastness, does not fade. Significantly extends the service life of galvanized roofs. Also Tikkurila Coatings, Temadur and Temalak coatings.

Question: Can chlorinated rubber paints protect metal from rust?

Answer: These paints are made from chlorinated rubber dispersed in organic solvents. In terms of their composition, they are classified as volatile resin and have high water and chemical resistance. Therefore, it is possible to use them to protect metal and concrete surfaces, water pipes and tanks from corrosion. From Tikkuril Coatings materials, you can use the Temanil MS-Primer + Temachlor system.

Anticorrosive in the bathhouse, bathtub, pool

Question: What kind of coating can protect bath containers for cold drinking and hot wash water from corrosion?

Answer: For containers for cold drinking and washing water, we recommend paint KO-42; Epovin for hot water - compositions ZinkKOS and Teplokor PIGMA.

Question: What are enamel pipes?

Answer: In terms of chemical resistance, they are not inferior to copper, titanium and lead, and their cost is several times cheaper. The use of enameled carbon steel pipes instead of stainless steel pipes results in 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 by brush or spray with the participation of professionals, or by brushing yourself. Preliminary preparation bath surface is to remove old enamel and clean off rust. The whole process takes no more than 4-7 hours, another 48 hours for the bath to dry, and you can use it after 5-7 days.

Re-enamel 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 bathtub, including hair varnishes, or to use bleach when washing. Such bathtubs are usually cleaned with soap products: washing powders or dishwashing detergents applied to a sponge or soft rag.

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

Answer: The “Svetlana” composition includes enamel, oxalic acid, hardener, and tinting pastes. The bath is washed with water, etched with oxalic acid (stains, stones, dirt, rust are removed and a rough surface is created). Wash with washing powder. Chips are repaired in advance. Then the enamel should be applied within 25-30 minutes. When working with enamel and hardener, contact with water is not allowed. Solvent – ​​acetone. Bath consumption – 0.6 kg; drying – 24 hours. Fully gains properties after 7 days.

You can also use two-component epoxy-based paint Tikkurila “Reaflex-50”. When using glossy bathtub enamel (white, tinted), either washing powders or laundry soap are used for cleaning. Fully gains properties after 5 days. Bath consumption – 0.6 kg. Solvent – ​​industrial alcohol.

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

Question: How to ensure protection against breakage of steel reinforcement in the bowl of a swimming pool?

Answer: If the condition of the pool's ring drainage is unsatisfactory, softening and suffusion of the soil is possible. 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 the point of breaking.

In such difficult cases, the reconstruction of damaged reinforced concrete tank structures 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-decaying fungi?

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

Question: What are the main sources of moisture in wood 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 (poles, piles, power 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 external wooden elements of buildings. Operating moisture in 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 a building when laying raw wood, using masonry mortars, concreting, etc. For example, 1 sq.m of laid wood with a moisture content of up to 23% releases up to 10 liters of water when it dries to 10-12%.

The wood of buildings, which dries naturally, is at risk of rotting for a long time. If chemical protection measures have not been provided, it is usually affected by 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 it is detected, as a rule, already when irreversible changes have occurred in the enclosing wooden structure or its element, for example, internal rotting.

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 combated with antiseptics. The exception is fungi (saprophytes), since antiseptics only affect 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 classify rot by color (red, white, gray, yellow, green and brown). Red rot affects coniferous trees, white and yellow rot affects oak and birch, green rot affects oak barrels, as well as wooden beams and cellar floors.

Question: Are there ways to neutralize porcini mushroom?

Answer: The white house mushroom is the most dangerous enemy of wooden structures. The speed at which wood is destroyed by porcini mushroom is such that in 1 month it completely “eats” a four-centimeter oak floor. Previously, in villages, if a hut was infected 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% chromium (5% solution of potassium dichromate in 5% sulfuric acid), while it is recommended to treat the ground with 0.5 m depth.

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

Answer: If the rotting process has already begun, it can only be stopped by thoroughly drying and ventilating wooden structures. In the early stages, disinfectant solutions, for example, such as the “Wood Healer” antiseptic compositions, can help. They are available in three different versions.

Mark 1 is intended for the prevention of wooden materials immediately after their purchase or immediately after building a house. The composition protects against fungus and wood-boring beetles.

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

Mark 3 is the most powerful antiseptic; it completely stops the rotting process. More recently, a special composition (grade 4) was developed to combat insects - “anti-bug”.

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

DULUX WEATHERSHIELD FUNGICIDAL WASH is a highly effective neutralizer of mold, lichen and rot. These compositions are used both indoors and outdoors, but they are effective only in the early stages of combating rot. In case of serious damage to wooden structures, it is possible to stop rotting using special methods, but this is quite complex work, usually performed by professionals using restoration chemical compounds.

Question: What protective impregnations and preservative compounds available on the domestic market prevent biocorrosion?

Answer: Of the Russian antiseptic drugs, it is necessary to mention metacid (100% dry antiseptic) or polysept (25% solution of the same substance). Such preservative compositions as “BIOSEPT”, “KSD” and “KSDA” 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. Textured coatings “AQUATEX”, “SOTEX” and “BIOX” eliminate the occurrence of fungus, mold and wood blue stains. They are breathable and have a durability of over 5 years.

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

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

Question: What are insecticides and how are they used?

Answer: To combat beetles and their larvae, poisonous chemical substances– contact and intestinal insecticides. Sodium fluoride and sodium fluoride are approved by the Ministry of Health and have been used since the beginning of the last century; When using them, safety precautions must be observed. To prevent damage to wood by the beetle, preventive treatment with silicofluoride compounds or a 7-10% solution of table salt is used. During historical periods of widespread wood 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 you can still find red beams.

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