Metals have been used by man since prehistoric times, products made from them are widespread in our lives. The most common metal is iron and its alloys. Unfortunately, they are prone to corrosion, or rusting—breaking down as a result of oxidation. Timely protection against corrosion allows you to extend the service life of metal products and structures.
Types of corrosion
Scientists have been struggling with corrosion for a long time and have identified several of its main types:
- Atmospheric. Oxidation occurs due to contact with atmospheric oxygen and water vapor contained in it. The presence in the air of pollutants in the form of chemically active substances accelerates rusting.
- Liquid. It takes place in the aquatic environment, the salts contained in water, especially sea water, greatly accelerate oxidation.
- Soil. Products and structures located in the ground are subject to this type. The chemical composition of the soil, groundwater and leakage currents create a special environment for the development of chemical processes.
Based on the environment in which the product will be operated, suitable methods of corrosion protection are selected.
Typical types of rust damage
There are the following characteristic types of corrosion damage:
- The surface is covered with a continuous rusty layer or separate pieces.
- Small areas of rust appeared on the part, penetrating into the thickness of the part.
- In the form of deep cracks.
- One of the components is oxidized in the alloy.
- Deep penetration throughout the volume.
- Combined.
Due to the occurrence, they are also divided:
- Chemical. Chemical reactions with active substances.
- Electrochemical. Upon contact with electrolytic solutions, an electric current arises, under the influence of which the electrons of metals are replaced, and the crystal structure is destroyed with the formation of rust.
Corrosion of metal and methods of protection against it
Scientists and engineers have developed many ways to protect metal structures from corrosion.
Corrosion protection of industrial and building structures, various types of transport is carried out by industrial methods.
Often they are quite complex and expensive. To protect metal products in household conditions, household methods are used that are more affordable and not associated with complex technologies.
Industrial
Industrial methods for protecting metal products are divided into a number of areas:
- Passivation. When steel is smelted, alloying additives such as Cr, Mo, Nb, Ni are added to its composition. They contribute to the formation of a strong and chemically resistant oxide film on the surface of the part, which prevents the access of aggressive gases and liquids to iron.
- Protective metal coating. A thin layer of another metal element - Zn, Al, Co, etc. is applied to the surface of the product. This layer protects the iron from rusting.
- Electrical protection. Plates made of another metal element or alloy, the so-called anodes, are placed next to the part to be protected. The currents in the electrolyte flow through these plates and not through the part. This is how underwater parts of sea transport and drilling platforms are protected.
- Inhibitors. Special substances that slow down or even stop chemical reactions.
- Protective paintwork.
- Heat treatment.
Corrosion protection methods used in the industry are very diverse. The choice of a specific corrosion control method depends on the operating conditions of the structure to be protected.
household
Household methods of protecting metals from corrosion are reduced, as a rule, to the application of protective paint and varnish coatings. Their composition can be very diverse, including:
- silicone resins;
- polymeric materials;
- inhibitors;
- small metal filings.
Rust converters are a separate group - compounds that are applied to structures already affected by corrosion. They restore iron from oxides and prevent re-corrosion. Converters are divided into the following types:
- Soils. They are applied to the cleaned surface, have high adhesion. They contain inhibitory substances in their composition, they allow saving the finishing paint.
- Stabilizers. Convert iron oxides to other substances.
- Converters of iron oxides to salts.
- Oils and resins that envelop rust particles and neutralize it.
When choosing a primer and paint, it is better to take them from the same manufacturer. So you will avoid problems of compatibility of paints and varnishes.
Protective paints for metal
According to the temperature regime of operation, paints are divided into two large groups:
- conventional, used at temperatures up to 80 ° C;
- heat resistant.
According to the type of binder base paints are:
- alkyd;
- acrylic;
- epoxy.
Metallic coatings have the following advantages:
- high-quality surface protection against corrosion;
- ease of application;
- drying speed;
- many different colors;
- long service life.
Hammer enamels are very popular, not only protecting the metal, but also creating an aesthetic appearance. Silver paint is also common for metal processing. Aluminum powder is added to its composition. Metal protection occurs due to the formation of a thin film of aluminum oxide.
Two-component epoxy mixtures are characterized by exceptional coating strength and are used for high stress assemblies.
Metal protection at home
To reliably protect metal products from corrosion, the following sequence of actions should be performed:
- clean the surface of rust and old paint with a wire brush or abrasive paper;
- degrease the surface;
- immediately apply a layer of soil;
- after the primer dries, apply two coats of base paint.
When working, use personal protective equipment:
- gloves;
- respirator;
- glasses or a transparent shield.
Methods for protecting metals from corrosion are constantly being improved by scientists and engineers.
Methods for resisting corrosion processes
The main methods used to resist corrosion are given below:
- increasing the ability of materials to resist oxidation by changing its chemical composition;
- isolation of the protected surface from contact with active media;
- decrease in the activity of the environment surrounding the product;
- electrochemical.
The first two groups of methods are used during the manufacture of the structure, and the second - during operation.
Methods for increasing resistance
Elements are added to the composition of the alloy that increase its corrosion resistance. Such steels are called stainless. They do not require additional coatings and are distinguished by their aesthetic appearance. Nickel, chromium, copper, manganese, cobalt in certain proportions are used as additives.
The resistance of materials to rust is also increased by removing corrosion-accelerating components, such as oxygen and sulfur from steel alloys, and iron from magnesium and aluminum alloys.
Reducing the aggressiveness of the environment and electrochemical protection
In order to suppress oxidation processes, special compounds, inhibitors, are added to the external environment. They slow down chemical reactions by tens and hundreds of times.
Electrochemical methods are reduced to changing the electrochemical potential of the material by passing an electric current. As a result, corrosion processes are greatly slowed down or even completely stopped.
Film protection
The protective film prevents active substance molecules from accessing the metal molecules and thus prevents corrosion phenomena.
Films are formed from paints, plastics and resins. Coatings are inexpensive and easy to apply. They cover the product in several layers. A layer of primer is applied under the paint, which improves adhesion to the surface and allows saving more expensive paint. Such coatings serve from 5 to 10 years. A mixture of manganese and iron phosphates is sometimes used as a primer.
Protective coatings are also created from thin layers of other metals: zinc, chromium, nickel. They are applied by electroplating.
Coating with a metal with a higher electrochemical potential than that of the base material is called anodic. It continues to protect the base material, diverting active oxidizers to itself, even in the event of partial destruction. Coatings with a lower potential are called cathodic. In the event of a violation of such a coating, it accelerates corrosion due to electrochemical processes.
The metal coating can also be applied by the plasma spray method.
Joint rolling of sheets of the base and protecting metal heated to the plasticity temperature is also used. Under pressure, mutual diffusion of the molecules of elements into each other's crystal lattices and the formation of a bimetallic material occurs. This method is called cladding.
Under the influence of external factors (liquids, gases, aggressive chemical compounds), any materials are destroyed. Metals are no exception. Corrosion processes cannot be completely neutralized, but it is quite possible to reduce their intensity, thereby increasing the service life of metal structures or others, which include "iron".
Methods of anti-corrosion protection
All methods of protection against corrosion can be conditionally classified as methods that are applicable either before the start of operation of the sample (group 1), or after its commissioning (group 2).
First
- Increased resistance to "chemical" exposure.
- Exclusion of direct contact with aggressive substances (surface insulation).
Second
- Reducing the degree of aggressiveness of the environment (depending on operating conditions).
- The use of EM fields (for example, the "imposition" of external e / currents, the regulation of their density and a number of other techniques).
The use of one or another method of protection is determined individually for each design and depends on several factors:
- type of metal;
- the conditions of its operation;
- the complexity of anti-corrosion measures;
- manufacturing capabilities;
- economic expediency.
In turn, all techniques are divided into active (implying a constant "impact" on the material), passive (which can be described as reusable) and technological (used at the stage of sample production).
Active
cathodic protection
It is advisable to use if the medium with which the metal is in contact is electrically conductive. The material is supplied (systematically or constantly) with a large “negative” potential, which makes it impossible in principle to oxidize it.
Protective protection
It consists in cathodic polarization. The sample is bound by contact with a material that is more susceptible to oxidation in a given conductive medium (tread). In fact, it is a kind of "lightning rod", taking on all the "negativity" that aggressive substances create. But such a protector needs to be periodically replaced with a new one.
Polarization anodic
It is used extremely rarely and consists in maintaining the "inertness" of the material in relation to external influences.
Passive (metal surface treatment)
Creating a protective film
One of the most common and low-cost methods of corrosion control. To create the surface layer, substances are used that must meet the following basic requirements - be inert with respect to aggressive chemical / compounds, do not conduct electric / current and have increased adhesion (good adhesion to the base).
All substances used at the time of metal processing are in a liquid or "aerosol" state, which determines the method of their application - painting or spraying. For this, paints and varnishes, various mastics and polymers are used.
Laying of metal structures in protective "chutes"
This is typical for different types of pipelines and communications of engineering systems. In this case, the role of an insulator is played by an air "layer" between the inner walls of the channel and the metal surface.
Phosphating
Metals are treated with special agents (oxidizers). They react with the base, resulting in the deposition of poorly soluble chemical/compounds on its surface. Quite an effective way to protect against moisture.
Coating with more resistant materials
Examples of the use of this technique are often found in everyday life products with chrome (), with silver, "galvanized" and the like.
As an option - protection with ceramics, glass, coating with concrete, cement mortars (coating) and so on.
Passivation
The point is to drastically reduce the chemical activity of the metal. To do this, its surface is treated with appropriate special reagents.
Reducing the aggressiveness of the environment
- The use of substances that reduce the intensity of corrosion processes (inhibitors).
- Air drying.
- Its chemical / purification (from harmful impurities) and a number of other methods that can be used in everyday life.
- Hydrophobization of the soil (backfilling, introduction of special substances into it) in order to reduce the aggressiveness of the soil.
Treatment with pesticides
It is used in cases where there is a possibility of the development of the so-called "biocorrosion".
Technological methods of protection
alloying
The most famous way. The point is to create an alloy based on metal that is inert with respect to aggressive influences. But it is realized only on an industrial scale.
As follows from the information provided, not all methods of anti-corrosion protection can be used in everyday life. In this regard, the possibilities of the "private trader" are significantly limited.
The main condition for the anticorrosion protection of metals and alloys is to reduce the corrosion rate. It is possible to reduce the corrosion rate by using various methods of protecting metal structures from corrosion. The main ones are:
1 Protective coatings.
2 Treatment of the corrosive environment to reduce corrosivity (especially with constant volumes of corrosive environments).
3 Electrochemical protection.
4 Development and production of new structural materials of increased corrosion resistance.
5 Transition in a number of designs from metal to chemically resistant materials (plastic high-molecular materials, glass, ceramics, etc.).
6 Rational design and operation of metal structures and parts.
1. Protective coatings
The protective coating must be continuous, evenly distributed over the entire surface, impervious to the environment, have high adhesion (adhesion strength) to the metal, be hard and wear-resistant. The coefficient of thermal expansion should be close to the coefficient of thermal expansion of the metal of the protected product.
The classification of protective coatings is shown in fig. 43
Protective coatings
Non-metallic Metal Coating Coatings
InorganicOrganicCathodeAnode
Figure 43 - Classification scheme for protective coatings
1.1 Metal coatings
The application of protective metal coatings is one of the most common methods of corrosion control. These coatings not only protect against corrosion, but also impart a number of valuable physical and mechanical properties to their surface: hardness, wear resistance, electrical conductivity, solderability, reflectivity, provide decorative finishes to products, etc.
According to the method of protective action, metal coatings are divided into cathodic and anodic.
Cathodic coatings have more positive, and anodic - more electronegative electrode potentials compared to the potential of the metal on which they are deposited. So, for example, copper, nickel, silver, gold, deposited on steel, are cathodic coatings, and zinc and cadmium in relation to the same steel are anode coatings.
It should be noted that the type of coating depends not only on the nature of the metals, but also on the composition of the corrosive medium. Tin in relation to iron in solutions of inorganic acids and salts plays the role of a cathode coating, and in a number of organic acids (food canned food) it serves as an anode. Under normal conditions, cathodic coatings protect the metal of the product mechanically, isolating it from the environment. The main requirement for cathode coatings is porosity. Otherwise, when the product is immersed in the electrolyte or when a thin film of moisture condenses on its surface, the exposed (in pores or cracks) areas of the base metal become anodes, and the coating surface becomes a cathode. In places of discontinuities, corrosion of the base metal will begin, which can spread under the coating (Fig. 44 a).
Figure 11 Scheme of corrosion of iron with a porous cathode (a) and anode (b) coating
Anode coatings protect the metal of the product not only mechanically, but mainly electrochemically. In the resulting galvanic cell, the coating metal becomes an anode and undergoes corrosion, and the exposed (in the pores) areas of the base metal act as cathodes and do not collapse as long as the electrical contact of the coating with the protected metal is maintained and sufficient current passes through the system (Fig. 4 b). Therefore, the degree of porosity of anode coatings, in contrast to cathodic coatings, does not play a significant role.
In some cases, electrochemical protection can take place during the application of cathodic coatings. This happens if the coating metal in relation to the product is an effective cathode, and the base metal is prone to passivation. The resulting anodic polarization passivates unprotected (in pores) areas of the base metal and makes it difficult to destroy them. This type of anodic electrochemical protection is manifested for copper coatings on steels 12X13 and 12X18H9T in sulfuric acid solutions.
The main method of applying protective metal coatings is galvanic. Thermal diffusion and mechanothermal methods, metallization by spraying and immersion in the melt are also used. Let us analyze each of the methods in more detail.
1.2 Electroplated coatings.
The galvanic method of deposition of protective metal coatings has become very widespread in industry. Compared with other methods of applying metal coatings, it has a number of serious advantages: high efficiency (metal protection from corrosion is achieved by very thin coatings), the possibility of obtaining coatings of the same metal with different mechanical properties, easy controllability of the process (controlling the thickness and properties of metal deposits by changes in the composition of the electrolyte and the electrolysis mode), the possibility of obtaining alloys of various compositions without the use of high temperatures, good adhesion to the base metal, etc.
The disadvantage of the galvanic method is the uneven thickness of the coating on products with a complex profile.
Electrochemical deposition of metals is carried out in a direct current galvanic bath (Fig. 45). The metal-plated product is hung on the cathode. As anodes, plates made of deposited metal (soluble anodes) or of a material insoluble in the electrolyte (insoluble anodes) are used.
An obligatory component of the electrolyte is a metal ion deposited on the cathode. The composition of the electrolyte may also include substances that increase its electrical conductivity, regulate the course of the anode process, ensure a constant pH, surfactants that increase the polarization of the cathode process, brightening and leveling additives, etc.
Figure 5 Electroplating bath for electrodeposition of metals:
1 - body; 2 - ventilation casing; 3 - coil for heating; 4 - insulators; 5 – anode rods; 6 – cathode rods; 7 - bubbler for mixing with compressed air
Depending on the form in which the discharging metal ion is in solution, all electrolytes are divided into complex and simple. The discharge of complex ions at the cathode occurs at a higher overvoltage than the discharge of simple ions. Therefore, deposits obtained from complex electrolytes are finer-grained and uniform in thickness. However, these electrolytes have a lower metal current efficiency and lower operating current densities, i.e. in terms of performance, they are inferior to simple electrolytes, in which the metal ion is in the form of simple hydrated ions.
The distribution of current over the surface of the product in a galvanic bath is never uniform. This leads to different deposition rates and, consequently, to different coating thicknesses in individual sections of the cathode. A particularly strong variation in thickness is observed on products with a complex profile, which adversely affects the protective properties of the coating. The uniformity of the thickness of the deposited coating improves with an increase in the electrical conductivity of the electrolyte, an increase in polarization with an increase in current density, a decrease in the current efficiency of the metal with an increase in current density, and an increase in the distance between the cathode and anode.
The ability of a galvanic bath to give uniform thickness coatings on a relief surface is called scattering power. Complex electrolytes have the highest scattering power.
To protect products from corrosion, galvanic deposition of many metals is used: zinc, cadmium, nickel, chromium, tin, lead, gold, silver, etc. Electrolytic alloys are also used, such as Cu - Zn, Cu - Sn, Sn - Bi and multilayer coatings.
The most effective (electrochemical and mechanical) protection of ferrous metals from corrosion is anodic coatings with zinc and cadmium.
Zinc coatings are used to protect against corrosion of machine parts, pipelines, steel sheets. Zinc is a cheap and readily available metal. It protects the main product by mechanical and electrochemical methods, since in the presence of pores or bare spots, zinc is destroyed, and the steel base does not corrode.
Zinc coatings dominate. Zinc protects about 20% of all steel parts from corrosion, and about 50% of the zinc produced in the world is used for electroplating.
In recent years, work has been developed on the creation of protective galvanic coatings from zinc-based alloys: Zn - Ni (8 - 12% Ni), Zn - Fe, Zn - Co (0.6 - 0.8% Co). In this case, it is possible to increase the corrosion resistance of the coating by 2-3 times.
Corrosion- a spontaneous process and, accordingly, proceeding with a decrease in the Gibbs energy of the system. The chemical energy of the reaction of the corrosion destruction of metals is released in the form of heat and dissipated in the surrounding space.
Corrosion leads to large losses as a result of the destruction of pipelines, tanks, metal parts of machines, ship hulls, offshore structures, etc. The irretrievable loss of metals from corrosion is 15% of their annual output. The goal of corrosion control is to conserve metal resources, the world's reserves of which are limited. The study of corrosion and the development of methods for protecting metals from it are of theoretical interest and are of great economic importance.
The rusting of iron in air, the formation of scale at high temperatures, the dissolution of metals in acids are typical examples of corrosion. As a result of corrosion, many properties of metals deteriorate: strength and ductility decrease, friction between moving parts of machines increases, and the dimensions of parts are violated. Distinguish between chemical and electrochemical corrosion.
Chemical, corrosion– destruction of metals by their oxidation in dry gases, in non-electrolyte solutions. For example, the formation of scale on iron at high temperature. In this case, the oxide films formed on the metal often prevent further oxidation, preventing further penetration of both gases and liquids to the metal surface.
electrochemical corrosion called the destruction of metals under the action of emerging galvanic pairs in the presence of water or another electrolyte. In this case, along with the chemical process - the release of electrons by metals, an electrical process also takes place - the transfer of electrons from one area to another.
This type of corrosion is divided into separate types: atmospheric, soil, corrosion under the action of "stray" current, etc.
Electrochemical corrosion is caused by impurities contained in the metal, or the heterogeneity of its surface. In these cases, when the metal comes into contact with the electrolyte, which can also be moisture adsorbed in air, many microgalvanic cells appear on its surface. . Anodes are metal particles cathodes– impurities and metal areas with a more positive electrode potential. The anode dissolves and hydrogen is released at the cathode. At the same time, the reduction of oxygen dissolved in the electrolyte is possible at the cathode. Therefore, the nature of the cathodic process will depend on some conditions:
acidic environment: 2H + + 2ē \u003d H 2 (hydrogen depolarization),
О 2 + 4Н + + 4ē → 2Н 2 О
neutral environment: O 2 +2H 2 O+4e - \u003d 4OH - (oxygen depolarization).
As an example, consider atmospheric corrosion iron in contact with tin. The interaction of metals with a drop of water containing oxygen leads to the appearance of a microvoltaic cell, the circuit of which has the form
(-)Fe|Fe 2+ || O 2 , H 2 O| sn (+).
The more active metal (Fe) is oxidized, donating electrons to copper atoms and goes into solution in the form of ions (Fe 2+). Oxygen depolarization occurs at the cathode.
Corrosion protection methods. All methods of corrosion protection can be divided into two large groups: non-electrochemical(alloying of metals, protective coatings, changing the properties of a corrosive environment, rational design of products) and electrochemical(project method, cathodic protection, anode protection).
Alloying of metals- this is an effective, albeit expensive, method of increasing the corrosion resistance of metals, in which components are introduced into the alloy composition that cause passivation of the metal. Chromium, nickel, titanium, tungsten, etc. are used as such components.
Protective coatings- these are layers artificially created on the surface of metal products and structures. The choice of coating type depends on the conditions in which the metal is used.
Materials for metal protective coatings can be pure metals: zinc, cadmium, aluminum, nickel, copper, tin, chromium, silver and their alloys: bronze, brass, etc. According to the nature of the behavior of metal coatings during corrosion, they can be divided into cathodic(for example, on steel Cu, Ni, Ag) and anode(zinc on steel). Cathodic coatings can protect the metal from corrosion only in the absence of pores and damage to the coating. In the case of anodic coating, the metal to be protected plays the role of a cathode and therefore does not corrode. However, the potentials of metals depend on the composition of the solutions; therefore, when the composition of the solution changes, the nature of the coating may also change. Thus, the coating of steel with tin in a solution of H 2 SO 4 is cathodic, and in a solution of organic acids it is anodic.
Non-metallic protective Coatings can be either inorganic or organic. The protective effect of such coatings is reduced mainly to the isolation of the metal from the environment.
Electrochemical protection method based on the inhibition of anodic or cathodic reactions of the corrosion process. Electrochemical protection is carried out by connecting to the protected structure (ship hull, underground pipeline), located in the electrolyte environment (sea, soil water), a metal with a more negative value of the electrode potential - protector.
For tens of hundreds of years, mankind has erected a large variety of technology around itself. But the era when people learned how to mine and process metal served as a start for such a wide development. Thanks to its properties, it became possible to reach great heights in technology, to build vehicles that could deliver a person to the other side of the world, weapons to defend themselves. But now technology has reached such a level that some mechanisms create others.
Despite the fact that metal is at the center of all (or almost all) technology, it is not the most perfect material. With the passage of time and the influence of the environment on it, it lends itself to rusting. This phenomenon causes more damage to this material, and as a result, worsens the operation of equipment, which can often lead to an accident or disaster. This article will explain everything about rusting steel, how this process occurs, and what to do to avoid (or eliminate) it.
What is rust?
"Rust" - this is the name of any kind of destruction of this material in everyday life. Specifically, these are the reddenings that form on the metal after reaction with oxygen. Oxidation adversely affects this material, making it brittle, loose edges, and reduce its hardness, as well as performance.
Therefore, many plants use different formulations to reduce friction, protect against corrosion and other negative environmental influences. More on this later. To move on to protecting against such exposure, gently understand how "rotting" affects steel, and how it kills its crystal lattice.
Natural destruction can cause a variety of damage:
- Complete damage;
- Violation of the density of the crystal lattice;
- Selective damage;
- Subsurface.
Depending on the nature of the damage, different methods of dealing with corrosion can be adopted. Each of the possible damage harms in its own way, and is unacceptable in various areas of technology and production. In the energy sector, such destruction is generally unacceptable (this can lead to gas leaks, the spread of radiation, and so on).
Video clip about what rust is and how to protect yourself from it:
Rust exposure
In order to effectively select mechanisms to counteract the destruction of the metal structure, it is necessary to understand how rust itself works. It can be of two types: chemical and electrochemical.
The first - chemical - can be attributed to the process of how the face of the sample is destroyed simply under the influence of the environment (gases most often). Such rust on metal takes a very long time to form and is usually very easy to avoid. The part must be cleaned and anti-corrosion coatings applied (paints, varnishes, etc.).
In addition, this process of iron deterioration occurs in humid, wet environments, as well as in contact with organic substances, such as oil, for example. The last case is especially important to consider, since rust on oil rigs is unacceptable.
Electrochemical corrosion is rarer and occurs in electrolytes. Only in this case, it is not the environment that is important, but the current that is produced as a result of electrization. It is he who destroys the metal and its surface (for the most part). Therefore, it can be easily distinguished by the crumbly surface of the metal.
To protect the metal from rust, you need to take into account all these features.
How to create the right protection?
Corrosion of metals and methods of protection are closely related. Therefore, all protection processes can be divided into just two groups: improving the metal during production, and applying protection during operation. The first includes changes in the chemical composition, which will make the part more resistant to environmental influences. Such equipment or items do not need additional protection.
The second group of protection includes various coatings and isolations of the working process. There are several ways to avoid destruction: avoid the environment that provokes it, or add something that will help get rid of the spread of metal damage, regardless of the environment and environment. At home, only the second option is possible, since a person without special equipment, an oven and other things simply cannot influence an already finished product.
How to Prepare for Rust
During the creation of metal products, there are two ways to remove corrosion or minimize its occurrence. To do this, substances (zinc, copper, and so on) that are resistant to gases and other negative irritants are either added to the structure. You can also often find the opposite effect.
As already mentioned, there is such a type of corrosion as selective. It destroys certain items in the item store. As you know, a metal consists of different atoms that form elements, each of which is susceptible to negative influences to a different extent. For example, in iron it is sulfur. In order for a part made of this material to serve as long as possible, sulfur is removed from its chemical composition, from which the selective separation of the structure begins. At home, such a reliable method is not possible.
Another anti-corrosion protection may be in production. During production, special coatings are applied that will protect the surface from external damage from a chemical reaction. The structural materials that are used in this case can only be in production, since it is almost impossible to purchase them in the public domain. In addition, such application is often carried out on automatic lines, which increases the reliability and speed of coating the material.
But no matter how the metal is improved, this material will still succumb to negative pressure from humidity, air, various gases, and will deteriorate during operation. Therefore, anti-corrosion protection is needed, which will not only affect it, but also protect it from the outside world.
Oxygen plays an important role in the spread of rust. The protection of metals from corrosion is also a slowdown, and not only prevention, of the spread of such a negative phenomenon. To do this, special molecules are introduced into the structure of the environment - inhibitors - which, penetrating into the surface of the metal, provide a kind of shield for it.
Anti-corrosion film is also often used, which can be applied in different ways. But it is easiest (and most reliable) when it is applied by spraying. Various polymeric materials, paints, enamels and the like are used for this. They also envelop the part and limit the access of the destructive environment to it. The fight against metal corrosion can be very diverse, despite the similarity in the process. This chemical process is inevitable, and almost always succeeds. That is why so much effort goes into preventing corrosion. Protection methods in view of this can be combined.
These are the main methods of protection. They are popular because of their simplicity, reliability and convenience. They also include coating with varnishes and enamels, but about this a little lower.
So, for example, before applying paint or enamel, workers lubricate the product with a primer so that the paint “lays down” on the surface better, and there is no moisture left between it and the product (which the primer absorbs). These methods of protecting metals from corrosion are not always done in production. Home tools are enough to do such operations yourself.
Anti-corrosion protection is sometimes very unusual. For example, when one metal is protected by another. This technique is often resorted to when the chemical alloy cannot be changed. Its surface is covered with another material, which is full of interspersed with elements that are resistant to corrosive influences. This so-called anti-corrosion layer helps to keep the surface of the more sensitive material very secure. For example, the coating may be of chromium.
This also includes the protective protection of metals from corrosion. In this case, the surface to be protected is coated with a metal that has low electrical conductivity (which is one of the main causes of corrosion). But this applies when contact with the environment is minimized. Therefore, such protection of metals from rust and other dangerous chemical processes is used in combination, for example, with inhibitors.
Such protection methods are used in order to avoid mechanical influences. It is difficult to say how to protect the metal most reliably. Each method can give its positive results.
How to get good coverage?
It is not always the responsibility of manufacturers to protect metal from corrosion. Often you need to take care of such a product yourself, and then the best scheme for improving the durability of the part is coating.
First of all, it must be completely clean. "Dirty" includes:
- Oil residue
- oxides
Eliminate them properly and completely. For example, you need to take a special liquid based on alcohol or gasoline so that the water does not additionally damage the structure. In addition, moisture may remain on the surface, and the paint applied on top of it simply will not perform its functions.
In a closed environment (between the surface and the paint), the corrosion of iron will develop even more actively, so such protection of the metal from corrosion will harm it rather than help it. Therefore, it is important to avoid moisture as well. After removing the dirt, it must be dried.
After that, you can apply the desired coating. But still it is the best way to protect against rust at home. Although there are different ways to protect metals from corrosion, you should always remember that using them incorrectly can lead to trouble. Therefore, there is no need to come up with something extraordinary, it is better to use already proven and reliable methods of protecting metals from corrosion.
It is also worth noting that the surface of the unit can be processed in several ways:
- Chemical
- electrochemical
- Mechanical
The latter is the simplest method of how to stop corrosion. The first two items from the list are more complex (in technical terms) processes, from which corrosion protection becomes more reliable. After all, they degrease the metal, which makes it more convenient for applying a protective coating on it. No more than 6-7 hours should pass before coating, since during this time contact with the medium will “restore” the previous result that was before processing.
Corrosion protection must be carried out - for the most part - at the plant and during production. But you don't have to rely on it alone. A homemade anti-corrosion agent won't hurt either.
Is it possible to permanently get rid of corrosion?
Despite the simplicity of the answer, it should be detailed. Corrosion and protection of metals from corrosion cannot be separated from each other, since they are based on the chemical composition of both the product itself and its surrounding atmosphere. No wonder the methods of combating corrosion are based precisely on these indicators. They either remove “weak” particles of the crystal lattice (or add more reliable inclusions to it), or they help to “hide” the surface of the product from gases and external influences.
Corrosion protection is nothing tricky. It is based on simple chemistry, and the laws of physics, which also indicate that it is impossible to avoid any processes in the interaction of elements. Anti-corrosion protection reduces the likelihood of such an outcome, increases the durability of the metal, but still - it does not completely save it. Whatever it is, it still needs to be updated, improved and combined, and additional methods of protecting metals from corrosion should be used.
It is possible to say how to prevent corrosion, but it is not worth it to strive to ensure that iron is not subject to it at all. The coating also lends itself to the destructive power of the surrounding world, and if this is not monitored, gases and moisture will reach the protected surface that is hidden under it. Corrosion and protection of metals is essential (both in production and during operation), but it also needs to be treated wisely.
