The development of the steel industry is inextricably linked with the search for ways and means to prevent the destruction of metal products. Protection against corrosion and the development of new techniques is a continuous process in the technological chain of production of metal and products made from it. Iron-containing products become unusable under the influence of various physical and chemical external environmental factors. We see these consequences in the form of hydrated iron residues, that is, rust.
Methods for protecting metals from corrosion are selected depending on the operating conditions of the products. Therefore it stands out:
- Corrosion associated with atmospheric phenomena. This is a destructive process of oxygen or hydrogen depolarization of a metal. Which leads to the destruction of the crystalline molecular lattice under the influence of a humid air environment and other aggressive factors and impurities (temperature, the presence of chemical impurities, etc.).
- Corrosion in water, primarily sea water. In it, the process goes faster due to the content of salts and microorganisms.
- Destruction processes that occur in the soil. Soil corrosion is a rather complex form of metal damage. Much depends on the composition of the soil, humidity, heating and other factors. In addition, products, for example, pipelines, are buried deep in the ground, which makes diagnostics difficult. And corrosion often affects individual parts pointwise or in the form of ulcerative veins.
Types of corrosion protection are selected individually, depending on the environment in which the metal product being protected will be located.
Typical types of rust damage
Methods for protecting steel and alloys depend not only on the type of corrosion, but also on the type of destruction:
- Rust covers the surface of the product in a continuous layer or in separate areas.
- It appears in the form of spots and penetrates pointwise into the depths of the part.
- Destroys the metal molecular lattice in the form of a deep crack.
- In a steel product consisting of alloys, destruction of one of the metals occurs.
- Deeper extensive rusting, when not only the surface is gradually damaged, but also penetration occurs into the deeper layers of the structure.
The types of damage can be combined. Sometimes they are difficult to determine immediately, especially when point destruction of steel occurs. Corrosion protection methods include special diagnostics to determine the extent of damage.
They produce chemical corrosion without generating electrical currents. Upon contact with petroleum products, alcohol solutions and other aggressive ingredients, a chemical reaction occurs, accompanied by gas emissions and high temperature.
Galvanic corrosion is when a metal surface comes into contact with an electrolyte, specifically water from the environment. In this case, diffusion of metals occurs. Under the influence of the electrolyte, an electric current arises, the replacement and movement of electrons of the metals that are included in the alloy occurs. The structure is destroyed and rust forms.
Steelmaking and its corrosion protection are two sides of the same coin. Corrosion causes enormous damage to industrial and commercial buildings. In cases with large-scale technical structures, for example, bridges, power poles, barrier structures, it can also provoke man-made disasters.
Metal corrosion and methods of protection against it
How to protect metal? There are many corrosion methods for metals and ways to protect against it. To protect metal from rust, industrial methods are used. In everyday life, various silicone enamels, varnishes, paints, and polymer materials are used.
Industrial
Protection of iron from corrosion can be divided into several main areas. Methods of protection against corrosion:
- Passivation. When producing steel, other metals are added (chromium, nickel, molybdenum, niobium and others). They are distinguished by increased quality characteristics, refractoriness, resistance to aggressive environments, etc. As a result, an oxide film is formed. These types of steel are called alloyed.
- Surface coating with other metals. Various methods are used to protect metals from corrosion: electroplating, immersion in a molten composition, application to the surface using special equipment. As a result, a metal protective film is formed. Chromium, nickel, cobalt, aluminum and others are most often used for these purposes. Alloys (bronze, brass) are also used.
- The use of metal anodes, protectors, often made of magnesium alloys, zinc or aluminum. As a result of contact with the electrolyte (water), an electrochemical reaction begins. The protector breaks down and forms a protective film on the surface of the steel. This technique has proven itself well for underwater parts of ships and offshore drilling rigs.
- Acid etching inhibitors. The use of substances that reduce the level of environmental impact on metal. They are used for preservation and storage of products. And also in the oil refining industry.
- Corrosion and protection of metals, bimetals (cladding). This is coating steel with a layer of another metal or a composite composition. Under the influence of pressure and high temperatures, diffusion and bonding of surfaces occurs. For example, well-known heating radiators made of bimetal.
Metal corrosion and methods of protection against it used in industrial production are quite diverse, such as chemical protection, glass enamel coating, and enameled products. Steel is hardened at high temperatures, over 1000 degrees.
On video: galvanizing metal as protection against corrosion.
Household
Protecting metals from corrosion at home is, first of all, chemicals for the production of paints and varnishes. The protective properties of the compositions are achieved by combining various components: silicone resins, polymer materials, inhibitors, metal powder and shavings.
To protect the surface from rust, it is necessary to use special primers or a rust converter before painting, especially old structures.
What types of converters are there:
- Primers - provide adhesion, adhesion to metal, level the surface before painting. Most of them contain inhibitors that significantly slow down the corrosion process. Preliminary application of a primer layer can significantly save paint.
- Chemical compounds - convert iron oxide into other compounds. They are not subject to rust. They are called stabilizers.
- Compounds that convert rust into salts.
- Resins and oils that bind and seal rust, thereby neutralizing it.
These products contain components that slow down the process of rust formation as much as possible. Converters are included in the product line of manufacturers producing metal paints. They vary in consistency.
It is better to choose primer and paint from the same company so that they match the chemical composition. You must first decide which methods you will choose to apply the composition.
Protective paints for metal
Metal paints are divided into heat-resistant, which can be used at high temperatures, and for normal temperatures up to eighty degrees. The following main types of metal paints are used: alkyd, acrylic, epoxy paints. There are special anti-corrosion paints. They are two- or three-component. They are mixed immediately before use.
Advantages of paintwork for metal surfaces:
- protect surfaces well from temperature changes and atmospheric fluctuations;
- can be applied quite easily in different ways (brush, roller, spray gun);
- most of them are quick-drying;
- wide range of colors;
- long service life.
Of the inexpensive means available, you can use ordinary silverware. It contains aluminum powder, which creates a protective film on the surface.
Two-component epoxy compounds are suitable for protecting metal surfaces that are subject to increased mechanical stress, in particular the underbody of cars.
Metal protection at home
Corrosion and methods of protecting against it at home require compliance with a certain sequence:
1. Before applying a primer or rust converter, the surface is thoroughly cleaned of dirt, oil stains, and rust. Use metal brushes or special attachments for grinders.
2. Then apply a primer layer, allow it to soak in and dry.
Protecting metals from corrosion is a complex process. It begins at the stage of steel smelting. It is difficult to list all the methods for combating rust, since they are constantly being improved, not only in industry, but also for domestic use. Manufacturers of paint and varnish products are constantly improving their compositions, increasing their corrosion properties. All this significantly extends the service life of metal structures and steel products.
Corrosion protection system: how and why?
The disadvantage of such a material as metal is that corrosion can occur on it. Today there are several methods, they need to be used in combination. The corrosion protection system will help get rid of rust and prevent the formation of layers.
Treating a metal surface with a special coating is an effective method. The metal coating increases the hardness and strength of the material and improves the mechanical properties. It should be borne in mind that in this case additional protection will be required. Non-metallic coating is applied to ceramics, rubber, plastic, wood.
Methods of protection against corrosion
Film-forming coatings are most often used; they are resistant to the external environment. A film forms on the surface, which inhibits corrosion processes.
In order to reduce corrosive activity, it is necessary to neutralize the environment exposed to its influence. Inhibitors will help you with this; they are introduced into an aggressive environment, and a film is formed that inhibits processes and changes the chemical parameters of the metal.
Alloying is widely used; it increases properties that help increase the resistance of the material to corrosion processes. Alloy steel contains a lot of chromium; it forms films that protect the metal.
It would be a good idea to use protective films. Anodic coatings are used for zinc and chromium, cathodic coatings are used for tin, nickel, and copper. They are applied using the hot method, and galvanization can also be used. The product must be placed in a container containing the protective metal in a molten state.
By using metallization, corrosion can be avoided. The surface is covered with metal, which is in a molten state, and it is sprayed with air. The advantage of this method is that it can be used to cover ready-made and fully assembled structures. The downside is that the surface will be a little rough. Such coatings are applied by diffusion into the base metal.
The coating can be protected with an oxide film, this procedure is called oxidation. The oxide film that exists on the metal is treated with a powerful oxidizing agent, as a result of which it becomes several times stronger.
Phosphating is also used in industry. Iron salts are immersed in a hot phosphate solution, eventually forming a surface film.
For temporary surface protection, it is necessary to use ethinol, technical petroleum jelly, and inhibitors. The latter slow down the reaction, resulting in corrosion developing much more slowly.
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 is an effective method of 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 enamels, metal oxides, compounds of chromium, phosphorus, etc. are used as inorganic coatings. 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 
Electrochemical protection of metal structures from corrosion is based on the imposition of a negative potential on the protected product. It demonstrates a high level of efficiency 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, before use, metal surfaces are necessarily 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 the cathodic potential, the metal potential shifts to the negative side, and with the anodic potential, it shifts to the positive side.
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. Oxidizers significantly increase the effect of the cathodic process on the steel surface, but they usually negatively affect the environment by releasing 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 of vehicles. Protecting the car body and some of its other elements from corrosion using 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 vehicle body itself.
Elementary methods of electrochemical protection of a car body:
- 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.
- 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.
The paint and varnish and galvanic coatings currently used for corrosion protection have significant drawbacks. As for paint and varnish coatings, first of all, these are a low degree of reliability in case of mechanical damage, a low resource of single-layer coatings and the high cost of multi-layer coatings. Damage to the coating to the protected metal leads to the development of under-film corrosion. In this case, the aggressive environment gets under the insulating layer of paint and varnish, and corrosion of the base metal begins, which actively spreads under the paint layer, which leads to peeling of the protective layer.
As for electroplating, once the required properties are achieved, the electrolyte is sensitive to temperature fluctuations throughout the deposition process, which usually lasts several hours. Electroplating also involves the use of materials and chemicals, many of which are quite harmful. Metallization and paint and varnish coatings compete with paint and varnish, galvanic, as well as glass-enamel, bitumen, bitumen-rubber, polymer and epoxy coatings and electrochemical protection. Spramet™.
Spramet™- a set of combined metallization and paint coatings for protection against corrosion for up to 50 years, each of which has additional properties - heat resistance, fire retardant characteristics, heat insulating characteristics, etc.
Spramet™ systems are applied both in production conditions and in repair conditions - at the site of operation of the facility. Spramet's high resistance to mechanical damage, the absence of under-film corrosion and prices comparable to high-quality painting make this system an ideal choice for long-term corrosion protection of especially dangerous and unique objects.
Under the influence of the main operational aging factors (time, combined temperature and moisture, aggressive environments, differences in electrochemical potentials), the system Spramet protection does not change its original properties, withstands heating up to 650°C, has high mechanical characteristics: wear resistance, flexibility, and also actively resists corrosion. Spramet effectively protects welds and retains its protective and decorative properties throughout the entire period of operation.
In total, the operating costs of products protected with Spramet systems are 2-4 times less compared to paint and varnish or other coatings known today.
CJSC "Plakart" conducted large-scale tests and began using compositions Spramet™— protective corrosion protection systems based on metal matrices. These compositions consist of one or more layers. The basis of the composition is a metal matrix: sprayed aluminum, zinc or their alloys. To improve performance properties, an impregnating layer is applied to close the pores, then a protective or heat-insulating layer, as well as a tinting layer.
IN JSC "Plakart" A line of compositions has been developed to solve problems under various operating conditions:
- Spramet-ANTIKOR
- Spramet-TERMO
- Spramet-NON-SLIP
- Spramet-NANO
Benefits compositions by Spramet are:
- higher hardness,
- resistance to abrasive wear.
To increase the protective properties, metal coatings are impregnated with special compounds. Spramet protection systems guarantee a service life of objects from 15 to 50 years of service without corrosion.
The corrosion resistance of Spramet compositions is due to the following factors:
- firstly, the base metallization layer of the Spramet system itself protects the surface well from corrosion;
- secondly, impregnation of the porous structure of the metal matrix with special compounds enhances the anti-corrosion properties of the system in a wide range of aggressive environments and temperatures;
- thirdly, if the Spramet composition is damaged before the protected material, another protection mechanism comes into play, namely a protector, which does not allow the development of under-film corrosion and delays local damage.
If the metal matrix is damaged in an aggressive environment, the protected metal and the coating metal form a galvanic couple in the presence of water. The potential difference in such a circuit is determined by the location of the metals in the electrochemical voltage series. Since the material being protected is typically ferrous metals, the coating material begins to be consumed, protecting the base metal and sealing the damaged area. In this case, the corrosion rate is determined by the difference in the electrode potentials of the pair. In addition, if the damage to the coating is minor (scratches), it is filled with oxidation products of the coating material, and the corrosion process stops or slows down significantly. For example, in sea and fresh water, aluminum and zinc are consumed at a rate of 3-10 microns per year, providing at least 25 years of corrosion resistance at a layer thickness of 250 microns.
The advantages of product processing protective compositions Spramet include the following:
- no restrictions on product sizes compared to hot-dip galvanizing and galvanizing;
- the ability to protect welds after installation of the structure (in the case of welding galvanized products, the quality of the seam deteriorates due to zinc compounds entering the weld pool);
- the possibility of applying Spramet protection in the field, which is not feasible either in the case of galvanizing or in the case of powder coating.
Some options for using the Spramet protection system
Spramet-ANTIKOR- Spramet-100 is a system that is resistant to corrosion and mechanical stress both under normal conditions and at temperatures up to 650°C.
- Spramet-130 is used for protection against corrosion in fresh water; it has good resistance to the effects of water of various compositions and the mechanical effects of ice.
- Spramet-150 is used for atmospheric corrosion, has good chemical resistance, and is used for storing petroleum products.
- Spramet-300 is used for atmospheric corrosion, operating temperatures up to 400°C, and has high adhesion.
- Spramet-310 is best used in heat and water supply facilities, and is resistant to inhibitors in water treatment systems.
- Spramet-320 is used in wastewater treatment plants for housing and communal services: it has high resistance to the effects of liquids with variable pH.
- Spramet-330 is used for atmospheric corrosion and corrosion in fresh water at operating temperatures up to 120°C; it is resistant to mechanical stress and has high adhesion.
- Spramet-430 is used for protection against atmospheric corrosion in the presence of chlorides, is resistant to deicing agents and has a decorative effect.
- Spramet-425 is best used for protection against corrosion in sea water, is resistant to mechanical stress, including ice, and has good resistance to chlorides.
Anti-corrosion high temperature system. Operating temperature - up to 650°C.
- Spramet-100 is a corrosion-resistant system both under normal conditions and at temperatures up to 650°C.
- Spramet-160. The metal matrix is coated with a certified fire retardant compound that foams when exposed to high temperatures and provides fire resistance of up to 60 minutes.
Due to the increased reliability and durability of the composition, Spramet is recommended for use when increased demands are placed on the protected object: a significant increase in the turnaround time or provision of anti-corrosion protection for the entire period of operation of metal structures, as well as in the absence of access to restore protective coatings.
Practical application (2011)
Specialists of ZAO Plakart have completed work on applying the system Spramet-100 for protection against corrosion of exhaust shafts of gas pumping units of the main gas pipeline system of OJSC Gazprom. The system is resistant to corrosion both under normal conditions and at temperatures up to 650°C, has an even white surface color, and is not afraid of mechanical damage, temperature changes and ultraviolet radiation.
Work on applying a corrosion-resistant system has been completed Spramet-300 on the crossbars of one of the cable-stayed bridges of the Alpika-Service Olympic route. Olympic venues operating in difficult climatic conditions require guaranteed long-term corrosion protection. System Spramet-ANTIKOR not only provides excellent protection against corrosion, but also serves as an excellent primer for paintwork.
Work on applying the protection system has been completed Spramet-150 on the internal surfaces of petroleum product storage tanks in the Astrakhan region. This anti-corrosion system was applied to tens of thousands of square meters of the internal surfaces of the tank and the pontoon floating in it.
From a standardization point of view "Spramet" system belongs to the group of combined metallization-paint and varnish coatings recommended for use on particularly dangerous and unique objects SNIP 2.03.11 “Protection of building structures from corrosion”, as well as many industry and ISO standards.
Quality system JSC "Plakart" certified according to ISO 9001. CJSC Plakart is a member of the self-regulatory organizations Zapaduralstroy and Sopkor. Trademark Spramet™ registered and owned by Plakart CJSC.
