All methods of metal corrosion protection, their pros and cons. Corrosion: types of corrosion, methods of protection What are the ways to protect metals from corrosion

The use of metal corrosion protection is a topical issue for many.

Corrosion, in fact, is a spontaneous process of destruction of metals, the cause of which is the adverse effects of the environment, as a result of which chemical, physico-chemical processes occur, leading to sad consequences.

Corrosion, acting on the metal, can completely destroy it. Therefore, it is necessary to deal with emerging rust.

And not only at the moment of its appearance. Preventive work to prevent the occurrence of corrosion in metals is also important.

According to their type, the following types of corrosion are distinguished:

• point;
• solid;
• through;
• spots or sores;
• layered;
• subsurface and others.

Corrosion occurs not only under the influence of water, but also soil, technical oil. As we can see, the types of corrosion are widely represented, but the methods of protection are not so numerous.

Anti-corrosion methods can be grouped based on the following methods:

1. electrochemical method - allows you to reduce the destructive process based on the law of electroplating;
2. reduction of the aggressive reaction of the production environment;
3. chemical resistance of metal;
4. protection of the metal surface from the adverse effects of the environment.

Surface protection and the galvanic method are used already at the time of operation of metal structures and products.

These include the following protection methods: cathodic, protective, and also inhibitory.

Electrochemical protection is based on the action electric current, under its constant influence corrosion stops.

The introduction of inhibitors into an aggressive environment that comes into contact with the metal makes it possible to reduce the rate of corrosion processes.

Chemical resistance and surface protection are among the film preservation methods. They can already be used both at the stage of manufacturing metal products, and at the time of operation.

The following methods are distinguished: tinning, galvanizing, painting, etc. Paint as a protective coating against rust is the most common and used method.

Protective anti-corrosion protection of metals

The basic principle that determines the tread protection is the transfer of the occurrence of corrosion from the main metal structure to a substitute.

That is, another metal with a negative electric potential is attached to the protected metal. The protector, being in working condition, collapses and is replaced by another.

Tread protection is relevant for structures that have been in neutral environments for a long time: water, earth, soil.

Zinc, magnesium, iron, aluminum are used as a protector. A striking example where tread protection is used is marine vessels that are constantly in the water.

Inhibitor

With the help of this tool, the aggressive effect of oils, acids, and other chemical liquids is reduced. It is used in pipelines, metal tanks.

It is presented in the form of a product that consists of boric acid with diethanolamine and vegetable oil. Included in diesel fuel, aviation kerosene.

With the help of an inhibitor, metals are well protected from corrosion in environments such as transformer oils, oil and hydrogen sulfide-containing masses.

However, the active base of this product is insoluble in mineral oil, and thus does not protect the metal from atmospheric corrosion.

Paint coating of metals

Paint is by far the most affordable and most used anti-corrosion material.

The paint coating creates a mechanical layer that creates an obstacle to the impact of an aggressive environment on a metal structure or product.

The paint can be used both before the appearance of rust and at the stage of corrosion.

In the second case, before applying the coating, the surface to be treated must be prepared: to clean the corrosion damage that has occurred, to seal the cracks, only after that the paint is applied, forming a protective layer.

With the help of this tool, they protect water pipes, metal elements of residential buildings - railings, partitions.

Another plus of this protection is that the paint can be different in color, therefore, the coating will also serve as decoration.

Joint use of anti-corrosion protection methods

Various anti-corrosion methods of metal protection can be used together. The most commonly used paintwork and protector.

Paint, in itself, is a rather impractical anti-corrosion material, since mechanical, water, air influences can damage its layer.

The protector will provide additional protection if the paintwork is broken.

Modern paint can simultaneously be a protector or an inhibitor. Protective protection occurs if the paint contains powder metals in its composition: aluminum, zinc, magnesium.

The inhibitor effect is achieved if the paint contains phosphoric acid.

Protection at work is determined by SNiP

In production, corrosion protection is an important point, since rust can lead not only to breakage, but also to disaster. SNiP 2.03.11 - 85 - this is the norm that enterprises should be guided by in order to prevent adverse consequences.

The conducted laboratory work made it possible to describe in the SNiP the types of corrosion damage, the sources of corrosion, as well as recommendations for ensuring the normal operation of metal structures.

In accordance with SNiP, the following protection methods are used:

• impregnation (sealing type) with materials with increased chemical resistance;
• pasting with film materials;
• using a variety of paint, mastic, oxide, metallized coatings.

Thus, SNiP makes it possible to apply all methods.

However, depending on where the structure is located, in what environment (highly aggressive, medium, weak or completely non-aggressive), SNiP specifies the use of protective equipment, and also specifies their composition.

At the same time, SNiP distinguishes yet another division of media into solid, liquid, gaseous, chemical and biologically active.

In fact, SNiP for each building material: aluminum, metal, steel, reinforced concrete and others, makes its own requirements.

Unfortunately, not all methods of protection are applicable to metals at home. The main method used is the coating of the product with paint.

The rest of the methods are used in production.

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 amounts 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 paintwork materials?

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 a significantly better corrosion resistance with a comparable layer thickness, less 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 use with 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 with 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: At 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: Corrosion resistance of thermal diffusion zinc coating is 3-5 times higher than that of galvanic coating and 1.5-2 times higher than that 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 "Konstanta 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 “over rust” include well-known materials: primer (some manufacturers produce it under the name “Inkor”) and primer-enamel “Gremirust”. These two-component epoxy paints (base + hardener) contain corrosion inhibitors and targeted additives, allowing 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 tank 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, using 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 is the spontaneous destruction of metals as a result of chemical or physico-chemical interaction with the environment. In the general case, this is the destruction of any material, whether it be metal or ceramics, wood or polymer.

Pure metals are most susceptible to corrosion. Alloys, plastics and other materials in this respect are characterized by the term "aging". Instead of the term "corrosion", the term "rust" is also often used.

Types of corrosion

The corrosion process spoils people's lives for many centuries, so it has been studied quite extensively. Exist various classifications corrosion depending on the type of environment, on the conditions of use of corrosive materials (whether they are energized, if they are in contact with another medium, then permanently or variablely, etc.) and on many other factors.

Electrochemical corrosion

Two different metals, interconnected, can corrode if, for example, condensate from the air gets on their joint. Different metals have different redox potentials and a galvanic cell is actually formed at the junction of the metals. In this case, the metal with a lower potential begins to dissolve, in this case, to corrode. This shows up at welds, around rivets and bolts.

To protect against this type of corrosion, for example, galvanizing is used. In a metal-zinc pair, zinc should corrode, but during corrosion, an oxide film forms on zinc, which greatly slows down the corrosion process.

Chemical corrosion

If the metal surface is in contact with a corrosive medium, and there are no electrochemical processes, then the so-called. chemical corrosion. For example, the formation of scale during the interaction of metals with oxygen at high temperatures.

Corrosion control

Despite the fact that ships with chests rotting at the bottom of the sea are not so bad for the environment, metal corrosion causes huge losses to people every year. Therefore, it is not surprising that for a long time there have been various methods of protecting metals from corrosion.

There are three types of corrosion protection:

Structural method includes the use of metal alloys, rubber gaskets, etc.

Active methods of corrosion control aimed at changing the structure of the electrical double layer. A constant electric field is applied using a constant current source, the voltage is selected in order to increase the electrode potential of the protected metal. Another method is to use a sacrificial anode, a more active material that will break down, protecting the item being protected.

Passive corrosion control- this is the use of enamels, varnishes, galvanization, etc. The coating of metals with enamels and varnishes is aimed at isolating metals from the environment: air, water, acids, etc. Galvanizing (as well as other types of spraying), in addition to physical isolation from the external environment, even if its layer is damaged, will not allow metal corrosion to develop, t .to. zinc corrodes more readily than iron (see "electrochemical corrosion" above).

Protective coatings can be applied to metal in various ways. Galvanization can be carried out in a hot shop, “on a cold one”, by thermal spraying. Painting with enamels can be done by spraying, roller or brush.

Much attention should be paid to preparing the surface for applying a protective coating. The success of the whole complex of corrosion protection measures largely depends on how well the metal surface is cleaned.

Modern protection of metals against corrosion is based on the following methods:

increasing the chemical resistance of structural materials,

isolation of the metal surface from an aggressive environment,

reducing the aggressiveness of the production environment,

reduction of corrosion by applying an external current (electrochemical protection).

These methods can be divided into two groups. The first two methods are usually implemented before the start of the production operation of a metal product (selection of structural materials and their combinations at the stage of design and manufacture of the product, application of protective coatings on it). The last two 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.

When applying the first two methods, the composition of steels and the nature of the protective coatings of a given metal product cannot be changed during its continuous operation in conditions of changing aggressiveness of the environment. The second group of methods allows, if necessary, to create new protection modes that ensure the least corrosion of the product when the operating conditions change. For example, in different sections of the pipeline, depending on the aggressiveness of the soil, different cathode current densities can be maintained or different inhibitors can be used for different types of oil pumped through pipes of a given composition.

However, in each case, it is necessary to decide which of the means or in which combination of them you can get the greatest economic effect.

The following main solutions for the protection of metal structures against corrosion are widely used:

1. Protective coatings

Metallic coatings.

According to the principle of protective action, anodic and cathodic coatings are distinguished. Anode coatings have a more negative electrochemical potential in an aqueous solution of electrolytes than a protected metal, while cathodic coatings have a more positive one. Due to the potential shift, anodic coatings reduce or completely eliminate the corrosion of the base metal in the pores of the coating, i.e. provide electrochemical protection, while cathodic coatings can enhance the corrosion of the base metal in the pores, but they are used, because they increase the physical and mechanical properties of the metal, such as wear resistance, hardness. However, this requires significantly greater coating thicknesses and, in some cases, additional protection.

Metal coatings are also divided according to the method of their production (electrolytic deposition, chemical deposition, hot and cold deposition, thermal diffusion treatment, sputtering, cladding).

Non-metallic coatings

These coatings are obtained by applying to the surface of various non-metallic materials - paint, rubber, plastic, ceramic, etc.

The most widely used paint and varnish coatings, which can be divided according to their purpose (weather-resistant, partially weather-resistant, water-resistant, special, oil and petrol resistant, chemically resistant, heat-resistant, electrically insulating, conservation) and according to the composition of the film former (bituminous, epoxy, organosilicon, polyurethane, pentaphthalic, etc.). )

Coatings obtained by chemical and electrochemical surface treatment

These coatings are films of insoluble products formed as a result of the chemical interaction of metals with external environment. Since many of them are porous, they are used primarily as undercoats for lubricants and paint coatings, increasing the protective ability of the coating on metal and providing reliable adhesion. Application methods - oxidation, phosphating, passivation, anodizing.

2. Treatment of a corrosive environment in order to reduce corrosivity.

Examples of such treatment are: neutralization or deoxygenation of corrosive environments, as well as the use of various types of corrosion inhibitors, which are introduced in small quantities into an aggressive environment and create an adsorption film on the metal surface that slows down electrode processes and changes the electrochemical parameters of metals.

3. Electrochemical protection of metals.

By cathodic or anodic polarization from an external current source or by connecting protectors to the protected structure, the metal potential is shifted to values ​​at which corrosion is greatly slowed down or completely stopped.

• 4. Development and production of new metal structural materials of increased corrosion resistance by removing impurities from the metal or alloy that accelerate the corrosion process (eliminating iron from magnesium or aluminum alloys, sulfur from iron alloys, etc.), or introducing new components into the alloy, greatly increasing corrosion resistance (for example, chromium in iron, manganese in magnesium alloys, nickel in iron alloys, copper in nickel alloys, etc.).
• 5. Transition in a number of designs from metal to chemically resistant materials (plastic high-polymer materials, glass, ceramics, etc.).
• 6. Rational design and operation of metal structures and parts (elimination of unfavorable metal contacts or their isolation, elimination of cracks and gaps in the structure, elimination of zones of moisture stagnation, impact of jets and sudden changes in flow rates in the structure, etc.).

The issues of designing anti-corrosion protection of building structures are given serious attention both in our country and abroad. When choosing design solutions, Western firms carefully study the nature of aggressive influences, the operating conditions of structures, the moral life of buildings, structures and equipment. At the same time, the recommendations of companies that produce materials for anticorrosion protection and have laboratories for research and processing of protective systems from their materials are widely used.

The relevance of solving the problem of anti-corrosion protection is dictated by the need to preserve natural resources and protect the environment. This problem is widely reflected in the press. Scientific papers, brochures, catalogs are published, international exhibitions in order to exchange experience between the developed countries of the world.

Thus, the need to study corrosion processes is one of the most important problems.

Cleaning and surface preparation

Ideal protection against corrosion is 80% ensured by proper surface preparation, and only 20% by the quality of the used paints and varnishes and the way they are applied.

1. Steel cleaning and rust removal

The duration and effectiveness of a coating on steel surfaces depends to a very large extent on how carefully the surface is prepared for painting.

Surface preparation consists of pre-treatment to remove scale, rust and foreign matter, if any, from a steel surface prior to the application of a shop primer or primer.

Secondary surface preparation aims to remove rust or foreign matter, if any, from a factory primed or primed steel surface prior to application of an anti-corrosion paint system.

The steel surface can be cleaned of rust in the following ways:

Wire brush cleaning:

Wire brushing, usually carried out with rotating wire brushes, is a common method not suitable for descaling, but suitable for preparing welds. The main disadvantage is that the treated surface is not completely freed from corrosion products and begins to shine and becomes greasy. This reduces the adhesion of primers and the effectiveness of the paint system.

Stump:

Pruning or mechanical chipping is usually carried out in combination with wire brushing. This is sometimes suitable for local repairs using conventional or specialty paint systems. It is not suitable for general surface preparation for painting with epoxy and chlorinated rubber based paints. Chiseling can be used to remove a thick layer of rust and provides savings in subsequent sandblasting.

Pneumatic hammer:

Remove rust, paint, etc. from corners and ledges to achieve a clean, rough surface.

Thermal way:

Flame cleaning of the surface involves the removal of rust by heat treatment using special equipment (acetylene or propane with oxygen). This eliminates almost all scale, but to a lesser extent rust. Therefore, this method cannot meet the requirements of modern paint systems.

Grinding:

Grinding involves the use of rotating wheels coated with abrasive material. It is used for minor repairs or to remove small foreign particles. The quality of these grinding wheels has been greatly improved and it can provide a good standard of surface preparation.

Mechanical cleaning:

A method of manual surface cleaning during which the primed and painted surface is roughened and any visible contamination is removed (with the exception of oil contamination and traces of rust).

light cleaning, purpose: roughening of the new surface

Abrasive: fine (0.2-0.5mm)

heavy cleaning (ISO Sa1), aim: removal of old coating layers

Abrasive: fine to medium (0.2-0.5/0.2-1.5mm)

Sandblasting:

Collision of a stream of abrasive material with a high kinetic energy, with a prepared surface. This process is controlled either manually by a jet or automatically by a paddle wheel and is the most thorough method of rust removal. Sandblasting by centrifuge, compressed air and vacuum are well known types.

The particles are only practically spherical and solid and should contain a minimum amount of foreign matter and irregularly shaped shots.

Primers used after blast cleaning should be tested for their performance.

coarse abrasive

The particles should have an angular shape with sharp cutting edges, the "halves" should be removed. Unless otherwise specified in the specification, sand of mineral origin must be used.

Wet (abrasive) (sandblasting) cleaning:

Wet cleaning under very high pressure

Pressure = more than 2000 bar

cleaning speed = max. 10-12 m2/hour depending on the material to be removed.

Use: Complete removal of all coatings and rust. The result is comparable to dry sandblasting, but with flashes of rust after drying.

High pressure wet cleaning

Pressure = up to 1300 bar

Cleaning speed = max. 5 m2/hour depending on the material to be removed. With much less pressure, this method is used to remove contaminants from any substrate.

Use: removal of salt and other contaminants, coatings and rust.

Wet abrasive low pressure sandblasting

Pressure= 6-8 kg/cm2

Cleaning speed = 10-16 m2/h depending on the material to be removed.

Uses: Reduce abrasiveness, reduce dust, remove salt, eliminate spark hazard. The result is comparable to dry sandblasting, but with flashes of rust after drying.

Steam Cleaning: Pressure=100-120kg/cm2

Use: Removal of water-soluble and emulsified soils: the substrate dries faster than when the substrate is treated with water.

ISO standards:

When determining the exact degree of rust removal and cleaning of a steel surface before painting, use international standard ISO 8501-01-1988 and ISO 8504-1992.

ISO 8501-01 is used for scale. This means the following levels of rust infestation:

A - steel surface heavily covered with scale, but little or no rust.

B - steel surface that has begun to rust and from which scale has begun to crumble.

C - steel surface from which the scale has fallen off and from where it can be removed, but with slight visible pitting.

D - steel surface from which the scale has fallen off, but with slight pitting, visible to the naked eye.

Grades of Surface Pretreatment The ISO standard defines seven grades of surface preparation.

The following standards are often used in specifications:

ISO-St Processing by hand and power tools.

Surface preparation by hand and with power tools: scraping, wire brushing, mechanical brushing and grinding, - denoted by the letters "St".

Before cleaning by hand or power tools, thick layers of rust must be removed by chipping. Visible contamination from oil, grease and dirt must also be removed.

After cleaning by hand and power tools, the surface must be free of loose paint and dust.

ISO-St2 Thorough cleaning by hand and power tools

When viewed superficially to the naked eye, the substrate should appear free from visible traces of oil, grease and dirt and from ill-adhering scale, rust, paint and foreign matter.

ISO-St3 Very thorough cleaning by hand and power tools

Same as for St2, but the substrate must be cleaned much more thoroughly until a metallic sheen appears.

ISO-Sa sandblasting

Surface preparation by sandblasting is indicated by the letters "Sa".

Before sandblasting can begin, thick layers of rust must be removed by chipping. Visible oil, grease and dirt must also be removed.

After sandblasting, the substrate must be free of dust and debris.

ISO-Sa1 light sandblasting

When inspected to the naked eye, the surface should appear free of visible oil, grease, and dirt, and of loose scale, rust, paint, and other foreign matter.

ISO-Sa2 Thorough sandblasting

When inspected to the naked eye, the surface should appear free from visible oil, grease, and dirt and from most scale, rust, paint, and other foreign matter. Each residual contamination must have a tight fit.

ISO-Sa2.5 Very thorough sandblasting

When inspected to the naked eye, the surface should appear free from visible oil, grease, and dirt and from most scale, rust, paint, and other foreign matter. All residual traces of infestation should only appear in the form of barely visible spots and streaks.

ISO-Sa3 Sandblasted to visually clean steel.

When inspected to the naked eye, the surface should appear free from visible oil, grease, and dirt and from most scale, rust, paint, and other foreign matter. The surface should have a uniform metallic sheen.

Surface roughness after sandblasting:

To determine the roughness, various designations are used, such as Rz, Rt Ra.

Rz - average elevation compared to the level of the plain = abrasive material profile

Rt - maximum elevation in relation to the level of the plain

Ra is the average distance to an imaginary center line that can be drawn between peaks and plains (ISO3274).

Abrasive profile (Rz) - 4 to 6 times C.L.A. (Ra)

Direct measurement of T.S.S. primers used on sandblasted steel up to 30 µm are very inaccurate. Primer with a dry film thickness of 30 microns or more forms an average thickness, and not a thickness at the tops.

When the Rz abrasive profile is mentioned in the specifications, sandblasting to ISO - Sa2.5 should be achieved using mineral sand unless otherwise mentioned.

Above Ra at 17 µm (abrasive profile R at T.C.C. 100 µm) an additional coat of primer is recommended to cover the roughness.

If heavily rusted steel is sandblasted, a profile in excess of 100 µm is often achieved.

Anticorrosion protection is required for any instrumental and structural products made of metal, since to one degree or another they all experience the negative corrosive effects of the environment around us.

1

Corrosion is understood as the destruction of the surface layers of steel and cast iron structures as a result of electrochemical and chemical effects. It simply spoils the metal, corrodes it, thereby making it unsuitable for subsequent use.

Experts have proven that every year about 10 percent of all metal mined on Earth is spent on covering losses (note that they are considered irretrievable) from corrosion leading to metal spraying, as well as to failure and damage to metal products.

Steel and cast iron structures at the first stages of corrosion reduce their tightness, strength, electrical and thermal conductivity, ductility, reflective potential and a number of other important characteristics. Subsequently, the structures become completely unusable.

In addition, corrosion phenomena are the cause of industrial and domestic accidents, and sometimes real environmental disasters. From rusted and leaky pipelines for oil and gas, a stream of compounds dangerous to human life and nature can rush at any moment. Given all of the above, anyone can understand the importance of high quality and effective corrosion protection using traditional and latest tools and methods.

It is impossible to completely avoid corrosion when it comes to steel alloys and metals. But it is quite possible to delay and reduce the negative consequences of rusting. For these purposes, there are now many anti-corrosion agents and technologies.

All modern methods Corrosion control can be divided into several groups:

• application of electrochemical methods of product protection;
• use of protective coatings;
• design and production of innovative, highly resistant to rusting structural materials;
• the introduction into the corrosive environment of compounds that can reduce the corrosive activity;
• rational construction and operation of parts and structures made of metals.

2

In order for the protective coating to cope with the tasks assigned to it, it must have a number of special qualities:

• be wear-resistant and as hard as possible;
• be characterized by a high index of adhesion strength with the surface of the workpiece (that is, have increased adhesion);
• have such a value of thermal expansion, which would differ slightly from the expansion of the protected structure;
• be as inaccessible to harmful environmental factors as possible.

Also, the coating should be applied to the entire structure as evenly as possible and in a continuous layer.

All protective coatings used today are divided into:

• metallic and non-metallic;
• organic and inorganic.

3

The most common and relatively uncomplicated option for protecting metals from rust, known for a very long time, is the use of paints and varnishes. Anticorrosion treatment of materials with such compounds is characterized not only by simplicity and low cost, but also by the following positive properties:

• the possibility of applying coatings of different color shades - which gives an elegant look to the structures, and reliably protects them from rust;
• the elementary nature of the restoration of the protective layer in case of its damage.

Unfortunately, paint and varnish compositions have a very low coefficient of thermal stability, low resistance in water and relatively low mechanical strength. For this reason, in accordance with existing SNiP, it is recommended to use them in cases where corrosion acts on products at a rate of not more than 0.05 millimeters per year, and their planned service life does not exceed ten years.

The components of modern paint and varnish compositions include the following elements:

• paints: suspensions of pigments with a mineral structure;
• varnishes: solutions (colloidal) of resins and oils in solvents of organic origin (corrosion protection in their application is achieved after polymerization of the resin or oil or their evaporation under the influence of an additional catalyst, as well as during heating);
• artificial and natural compounds called film formers (for example, drying oil is perhaps the most popular non-metallic "protector" of cast iron and steel);
• enamels: lacquer solutions with a complex of selected pigments in crushed form;
• softeners and various plasticizers: adipic acid in the form of esters, dibutyl phtholate, castor oil, tricresyl phosphate, rubber, and other elements that increase the elasticity of the protective layer;
• ethyl acetate, toluene, gasoline, alcohol, xylene, acetone and others (these components are needed so that paint and varnish compositions can be applied to the treated surface without problems);
• inert fillers: the smallest particles of asbestos, talc, chalk, kaolin (they make the anti-corrosion capabilities of the films higher, and also reduce the waste of other components of paint and varnish coatings);
• pigments and paints;
• catalysts (in the language of professionals - driers): cobalt and magnesium salts of fatty organic acids necessary for the rapid drying of protective compounds.

Paint and varnish compounds are selected taking into account the conditions under which the workpiece is operated. Compositions based on epoxy elements are recommended for use in atmospheres where chloroform and divalent chlorine vapors are constantly present, as well as for processing structures in various acids (nitric, phosphoric, hydrochloric, etc.).

Paints and varnishes with polyvinyl are also resistant to acids. They are also used to protect the metal from the effects of oils and alkalis. But to protect structures from gases, compounds based on polymers (epoxy, organofluorine and others) are more often used.

When choosing a protective layer, it is very important to take into account the requirements of Russian SNiP for various industries. Such standards clearly indicate which compositions and methods of corrosion protection can be used, and which ones should be abandoned. For example, SNiP 3.04.03-85 sets out recommendations for protecting various building structures:

• main gas and oil pipelines;
• casing pipes made of steel;
• heating mains;
• reinforced concrete and steel structures.

4

On metal products, it is quite possible to form special films by means of electrochemical or chemical processing to protect them from rust. Most often, phosphate and oxide films are created (again, the provisions of SNiP must be taken into account, since the protection mechanisms for such compounds are different for different products).

Phosphate films are suitable for anti-corrosion protection of non-ferrous and ferrous metals. The essence of this process is to immerse products in a solution of zinc, iron or manganese with acidic phosphorus salts heated to a certain temperature (around 97 degrees). The resulting film is ideal for applying a paint composition on it.

Note that the phosphate layer itself does not have a long service life. It is thin and not very durable. Phosphating is used to protect parts that operate at high temperatures or in salt water (for example, sea water).

Oxide protective films are also used to a limited extent. They are obtained by processing metals in alkali solutions under the influence of current. A known solution for oxidation is sodium hydroxide (four percent). The operation of obtaining an oxide layer is often called bluing, since on the surface of low- and high-carbon steels the film is characterized by a beautiful black color.

Oxidation is performed in situations where the initial geometric parameters must be kept unchanged. The oxide layer is usually applied to precision instruments, small arms. The thickness of such a film in most cases does not exceed one and a half microns.

Other methods of corrosion protection using inorganic coatings:

5

If metal products are subjected to polarization, the rate of rusting due to electrochemical factors can be significantly reduced. There are two types of electrochemical anti-corrosion protection:

• anode;
• cathodic.

Anode technology is suitable for materials from:

• alloys (high-alloyed) based on iron;
• with a low level of doping;
• carbon steels.

The essence of the anode protection technique is simple: metal product, which needs to be given anti-corrosion properties, is connected to the cathode protector or to the "plus" of the (external) current source. This procedure reduces the rate of rusting by several thousand times. Elements and compounds with a high positive potential (lead, platinum, lead dioxide, platinized brass, tantalum, magnetite, carbon, and others) can act as a cathode protector.

Anode anti-corrosion protection will only be effective if the structural processing apparatus meets the following requirements:

• there are no rivets on it;
• welding of all elements is performed with the highest quality;
• metal passivation is carried out in a technological environment;
• the number of gaps and slots is minimal (or they are absent).

The described type of electrochemical protection is unsafe due to the risk of active anodic dissolution of structures during the suspension of the current supply. In this regard, it is carried out only when there is a special system for monitoring the implementation of all the stipulated technological scheme operations.

More common and less dangerous is cathodic protection, which is suitable for metals that do not have a tendency to passivate. A similar method involves connecting the structure to the electrode negative potential or to the "minus" of the current source. Cathodic protection is used for the following types equipment:

• tanks and devices (their internal parts) operated at chemical enterprises;
• drilling rigs, cables, pipelines and other underground structures;
• elements of coastal structures that come into contact with salt water;
• mechanisms made of high-chromium and copper alloys.

The anode in this case is coal, cast iron, scrap metal, graphite, steel.

6

In manufacturing plants, corrosion can be successfully dealt with by modifying the composition of the aggressive atmosphere in which metal parts and structures operate. There are two options for reducing the aggressiveness of the environment:

• the introduction of corrosion inhibitors (retarders) into it;
• removal from the environment of those compounds that are the cause of corrosion.

Inhibitors are typically used in cooling systems, tanks, pickling baths, tanks, and other systems where the volume of the corrosive medium is approximately constant. Retarders are divided into:

• organic, inorganic, volatile;
• anode, cathode, mixed;
• working in alkaline, acidic, neutral environment.

Below are the most famous and commonly used corrosion inhibitors that meet the requirements of SNiP for various production facilities:

• calcium bicarbonate;
• borates and polyphosphates;
• bichromates and chromates;
• nitrites;
• organic moderators (polybasic alcohols, thiols, amines, amino alcohols, amino acids with polycarboxylic properties, volatile compounds "IFKhAN-8A", "VNH-L-20", "NDA").

But to reduce the aggressiveness of the corrosive atmosphere, you can use the following methods:

• vacuuming;
• neutralization of acids with caustic soda or lime (slaked);
• deaeration to remove from oxygen.

As you can see, today there are many ways to protect metal structures and products. It is only important to correctly select the best option for each specific case, and then parts and structures made of steel and cast iron will serve for a very, very long time.

7

We want to very briefly review the SNiP data describing the requirements for rust protection of building (aluminum, metal, steel, reinforced concrete and other) structures. They give recommendations on the use of various methods of anti-corrosion protection.

SNiP 2.03.11 provide for the protection of surfaces of building structures in the following ways:

• impregnation (sealing type) with materials with increased chemical resistance;
• pasting with film materials;
• using a variety of paint, mastic, oxide, metallized coatings.

In fact, these SNiP allow you to use all the methods of protecting metals from rust that we have described. At the same time, the rules stipulate the composition of specific protective equipment, depending on the environment in which the building is located. From this point of view, environments can be: medium, slightly and strongly aggressive, as well as completely non-aggressive. Also in SNiP, the division of media into biologically and chemically active, into solid, liquid and gaseous is accepted.