Topic: Corrosion of metals. By type of corrosive environment

There are a lot of different factors that can significantly damage metal. At the same time, all metals corrode in one way or another and have some defects. For example, you should not join copper and aluminum if they are part of electrical wiring. This is because such a small electrolyzer is formed, which little by little eats away the metal. As a result, heating occurs, and ultimately an arc strike, which can lead to a fire. Some metals, like tin, tend to decay. This is the so-called tin plague. This can happen, for example, due to low temperature. But steel is most susceptible to corrosion. Steel, if it is not alloyed, that is, mixed with chromium, tends to rust. And rust is the most terrible enemy of steel and iron. It has several features that can simply destroy metal.

In fact, there are a lot in various ways, which can prevent metal corrosion. In some cases, this can help, but sometimes it is pointless. To prevent corrosion, there is a special anti-corrosion primer enamel, which prevents and prevents rust. But is it really that dangerous? Let's understand a little about this and how you can prevent rust.

Why is rust dangerous?

Rust is the decay of steel or iron. When iron and moisture come into contact, a chemical reaction occurs that turns the metal into corrosion. Because of this, it turns out that the metal loses its strength and becomes softer. This is dangerous for all metal structures as it becomes thinner. Long-term rusting can cause even very thick metal beams to collapse. In addition, it significantly spoils the appearance, especially if the metal has some decorative meaning.

Ways to prevent

For tools, regular oil or special lubricant is usually used. Thus, contact between metal and moisture is prevented. Thanks to this, no corrosion occurs. But large structures are difficult to coat with oil. That's why they are covered with enamel. You can buy them at the link http://www.untec.ru, where there are big choice. The main point of enamel is that it applies like paint. It holds up much better and can be used on reinforced concrete or other materials. An excellent material that can even be used without a primer, as it adheres well even without it.

Corrosion is the destruction of metal, ceramic, wood and other materials as a result of chemical or physical-chemical interaction. As for the reasons for the occurrence of such an undesirable effect, they are different. In most cases, this is structural instability to thermodynamic influences environment. Let's take a closer look at what corrosion is. Types of corrosion also need to be considered, and it wouldn’t hurt to talk about protection against it.

Some general information

We are used to hearing the term “rusting”, which is used in the case of corrosion of metal and alloys. There is also such a thing as “aging” - it is characteristic of polymers. Essentially, it's the same thing. A striking example is the aging of rubber products due to active interaction with oxygen. In addition, some plastic elements are destroyed by exposure. The rate of corrosion directly depends on the conditions in which the object is located. Thus, rust on a metal product will spread faster the higher the temperature. Humidity also affects: the higher it is, the faster it becomes unsuitable for further use. It has been experimentally established that approximately 10 percent of metal products are irretrievably written off, and corrosion is to blame. Types of corrosion are different and are classified depending on the type of environment, the nature of the course, etc. Let's look at them in more detail.

Classification

Currently, there are more than two dozen rusting options. We will present only the most basic types of corrosion. Conventionally, they can be divided into the following groups:

Chemical corrosion is a process of interaction with a corrosive environment, in which the reduction of the oxidizing agent occurs in one act. The metal and the oxidizing agent are not separated spatially.
Electrochemical corrosion is the process of interaction of a metal with the ionization of atoms and the reduction of the oxidizing agent in different acts, but the rate largely depends on the electrode potential.
Gas corrosion - chemical rusting of metal with a minimum moisture content (no more than 0.1 percent) and/or high temperatures in a gaseous environment. Most often this species is found in the chemical and oil refining industries.

In addition, there are still a huge number of rusting processes. All of them are corrosion. Types of corrosion, in addition to those described above, include biological, radioactive, atmospheric, contact, local, targeted rusting, etc.

Electrochemical corrosion and its features

With this type of destruction, the process occurs when the metal comes into contact with the electrolyte. The latter can be condensate or rainwater. The more salts and acids a liquid contains, the higher the electrical conductivity, and therefore the speed of the process. As for the places of metal structures most susceptible to corrosion, these are rivets, welded joints, and places of mechanical damage. If the structural properties of the iron alloy make it resistant to rust, the process slows down somewhat, but still continues. A striking example is galvanizing. The fact is that zinc has a more negative potential than iron. For this simple reason, the iron alloy is restored, but the zinc alloy is corroded. However, the presence of an oxide film on the surface greatly slows down the destruction process. Of course, all types of electrical chemical corrosion are extremely dangerous and sometimes it is even impossible to fight them.

Chemical corrosion

This change in metal is quite common. A striking example is the appearance of scale as a result of the interaction of metal products with oxygen. High temperature in this case acts as an accelerator of the process, and liquids such as water, salts, acids, alkalis and salt solutions can participate in it. If we talk about materials such as copper or zinc, their oxidation leads to the formation of a film that is resistant to further corrosion. Steel products form iron oxides. Further developments lead to the appearance of rust, which does not provide any protection against further destruction, but on the contrary, contributes to it. Currently, all types of chemical corrosion are eliminated using galvanization. Other means of protection may also be used.

Types of concrete corrosion

Changes in the structure and increase in the fragility of concrete under the influence of the environment can be of three types:

Destruction of parts of cement stone is one of the most common types of corrosion. It occurs when a concrete product is systematically exposed to precipitation and other liquids. As a result, calcium oxide hydrate is washed out and the structure is disrupted.
Interaction with acids. If cement stone comes into contact with acids, calcium bicarbonate is formed - an aggressive chemical element for a concrete product.
Crystallization of sparingly soluble substances. In essence, this means biocorrosion. The bottom line is that microorganisms (spores, fungi) enter the pores and develop there, resulting in destruction.

Corrosion: types, methods of protection

Billions of dollars in annual losses have led people to fight against these harmful effects. We can say with confidence that all types of corrosion lead to the loss not of the metal itself, but of valuable metal structures, the construction of which costs a lot of money. It is difficult to say whether it is possible to provide 100% protection. However, with proper surface preparation, which consists of abrasive blasting, good results can be achieved. The paint coating reliably protects against electrochemical corrosion when applied correctly. And special surface treatment will reliably protect against metal destruction underground.

Active and passive methods of control

The essence active methods is to change the structure of the double electric field. For this purpose, a direct current source is used. The voltage must be selected in such a way that the product to be protected increases. Another extremely popular method is the “sacrificial” anode. It breaks down, protecting the base material.

Passive protection involves the use of paint and varnish. The main task is to completely prevent moisture and oxygen from entering the protected surface. As noted above, it makes sense to use zinc, copper or nickel plating. Even a partially destroyed layer will protect the metal from rusting. Of course, these types of protection against metal corrosion are effective only when the surface does not have visible defects in the form of cracks, chips, and the like.

Galvanizing in detail

We have already looked at the main types of corrosion, and now I would like to talk about the best methods of protection. One of these is galvanizing. Its essence lies in the fact that zinc or its alloy is applied to the surface being treated, which gives the surface some physical and chemical properties. It is worth noting that this method is considered one of the most economical and efficient, and this despite the fact that approximately 40 percent of the world's production of this element is spent on zinc metallization. Steel sheets, fasteners, as well as instruments and other metal structures can be galvanized. The interesting thing is that using metallization or spraying you can protect a product of any size and shape. Zinc has no decorative purpose, although with the help of some special additives it becomes possible to obtain shiny surfaces. In principle, this metal is capable of providing maximum protection in aggressive environments.

Conclusion

So we told you about what corrosion is. Types of corrosion were also considered. Now you know how to protect the surface from premature rusting. By and large, this is extremely simple to do, but where and how the product is used is of considerable importance. If it is constantly subjected to dynamic and vibration loads, then there is a high probability of cracks in the paintwork, through which moisture will enter the metal, as a result of which it will gradually deteriorate. However, the use of various rubber gaskets and sealants in areas where metal products interact can slightly extend the life of the coating.

Well, that's all on this topic. Remember that premature failure of a structure due to corrosion can lead to unforeseen consequences. At an enterprise, large material damage and human casualties are possible as a result of rusting of the supporting metal structure.

physical-chemical or chemical interaction between a metal (alloy) and the environment, leading to deterioration of the functional properties of the metal (alloy), environment or technical system incorporating them.

The word corrosion comes from the Latin “corrodo” “to gnaw” (Late Latin “corrosio” means “corrosion”).

Corrosion is caused by a chemical reaction between the metal and environmental substances that occurs at the interface between the metal and the environment. Most often, this is the oxidation of the metal, for example, by atmospheric oxygen or acids contained in solutions with which the metal is in contact. Metals located in the voltage series (activity series) to the left of hydrogen, including iron, are especially susceptible to this.

As a result of corrosion, iron rusts. This process is very complex and includes several stages. It can be described by the summary equation:

Fe + 6 H 2 O (moisture) + 3 O 2 (air) = 4 Fe (OH ) 3

Iron hydroxide(

III ) is very unstable, quickly loses water and turns into iron oxide ( III ). This compound does not protect the iron surface from further oxidation. As a result, the iron object can be completely destroyed.

Many metals, including quite active ones (for example, aluminum), when corroded, become covered with a dense, well-bonded oxide film, which does not allow oxidizing agents to penetrate into deeper layers and therefore protects the metal from corrosion. When this film is removed, the metal begins to interact with moisture and oxygen in the air.

Aluminum under normal conditions is resistant to air and water, even boiling water, but if mercury is applied to the surface of aluminum, the resulting amalgam destroys the oxide film pushes it from the surface, and the metal quickly turns into white flakes of aluminum metahydroxide:

4Al + 2H 2 O + 3O 2 = 4AlO(OH)Amalgamated aluminum reacts with water to release hydrogen: Al + 4 H 2 O = 2 AlO (OH) + 3 H 2

Some rather inactive metals are also susceptible to corrosion. In humid air, the surface of copper becomes covered with a greenish coating (patina) as a result of the formation of a mixture of basic salts.

Sometimes when metals corrode, it is not oxidation that occurs, but the reduction of some elements contained in the alloys. For example, at high pressures and temperatures, carbides contained in steels are reduced by hydrogen.

The destruction of metals in the presence of hydrogen was discovered in the mid-nineteenth century. The French engineer Sainte-Claire Deville studied the causes of unexpected ruptures of gun barrels. During their chemical analysis, he found hydrogen in the metal. Deville decided that it was hydrogen saturation that was the reason for the sudden drop in the strength of steel.

Hydrogen caused a lot of trouble to the designers of equipment for one of the most important industrial chemical processes - ammonia synthesis. The first devices for this synthesis lasted only tens of hours, and then shattered into small parts. Only adding titanium, vanadium or molybdenum to steel helped solve this problem.

Corrosion of metals can also include their dissolution in liquid molten metals (sodium, lead, bismuth), which are used, in particular, as coolants in nuclear reactors.

In terms of stoichiometry, the reactions that describe the corrosion of metals are quite simple, but in terms of their mechanism they belong to complex heterogeneous processes. The corrosion mechanism is determined primarily by the type of aggressive environment.

When a metal material comes into contact with a chemically active gas, a film of reaction products appears on its surface. It prevents further contact between metal and gas. If counter diffusion of reacting substances occurs through this film, then the reaction continues. The process is facilitated at high temperatures. During corrosion, the product film continuously thickens and the metal is destroyed. Metallurgy and other industries that use high temperatures suffer heavy losses from gas corrosion.

Corrosion is most common in electrolyte environments. In some technological processes, metals come into contact with molten electrolytes. However, most often corrosion occurs in electrolyte solutions. The metal does not have to be completely immersed in the liquid. Electrolyte solutions can be present in the form of a thin film on the surface of the metal. They often permeate the environment surrounding the metal (soil, concrete, etc.).

During the construction of the metro bridge and the Leninskie Gory station in Moscow, large amounts of sodium chloride were added to the concrete to prevent freezing of the concrete that had not yet set. The station was built in the shortest possible time (in just 15 months) and opened on January 12, 1959. However, the presence of sodium chloride in the concrete caused the destruction of the steel reinforcement. 60% of reinforced concrete structures were subject to corrosion, so the station was closed for reconstruction , lasting almost 10 years. Only on January 14, 2002, the metro bridge and the station, called “Vorobyovy Gory,” were re-opened.

Using salts (usually sodium or calcium chloride) to remove snow and ice from roads and sidewalks also causes metals to degrade faster. Vehicles and underground communications are severely affected. It is estimated that in the United States alone, the use of salts to combat snowfall and ice leads to losses of about $2 billion per year due to engine corrosion and $0.5 billion in additional repairs of roads, underground highways and bridges.

In electrolyte environments, corrosion is caused not only by the action of oxygen, water or acids on metals, but also by electrochemical processes. Already at the beginning of the 19th century. Electrochemical corrosion was studied by English scientists Humphry Davy and Michael Faraday. The first theory of electrochemical corrosion was put forward in 1830 by the Swiss scientist De la Rive. It explained the occurrence of corrosion at the point of contact between two different metals.

Electrochemical corrosion leads to the rapid destruction of more active metals, which in various mechanisms and devices come into contact with less active metals located to the right in the electrochemical voltage series. The use of copper or brass parts in iron or aluminum structures that operate in seawater significantly increases corrosion. There are known cases of destruction and sinking of ships whose iron plating was fastened with copper rivets.

Separately, aluminum and titanium are resistant to seawater, but if they come into contact in one product, for example, in a housing for underwater photographic equipment, the aluminum very quickly breaks down and the housing leaks.

Electrochemical processes can also occur in a homogeneous metal. They are activated if there are differences in the composition of the metal grain in the bulk and at the boundary, inhomogeneous mechanical stress, microimpurities, etc. In developing general theory Many of our compatriots participated in electrochemical corrosion of metal materials, including Vladimir Aleksandrovich Kistyakovsky (1865-1952) and Alexander Naumovich Frumkin (1895-1976).

One of the reasons for the occurrence of electrochemical corrosion is stray currents, which appear due to the leakage of part of the current from electrical circuits into the soil or aqueous solutions, where they fall on metal structures. Where the current exits these structures, the dissolution of the metal begins again into the soil or water. Such zones of destruction of metals under the influence of stray currents are especially often observed in areas of ground electric transport (tram lines, electric railway transport). These currents can reach several amperes, which leads to large corrosion damage. For example, the passage of a current of 1 A for one year will cause the dissolution of 9.1 kg of iron, 10.7 kg of zinc, 33.4 kg of lead.

Corrosion can also occur under the influence of radiation, as well as waste products of bacteria and other organisms. The development of bacteria on the surface of metal structures is associated with the phenomenon of biocorrosion. The fouling of the underwater part of ships with small marine organisms also affects corrosion processes.

With simultaneous exposure to metal external environment and mechanical stresses, all corrosion processes are activated, since this reduces the thermal stability of the metal, destroys oxide films on the metal surface, and intensifies electrochemical processes in places where cracks and inhomogeneities appear.

Corrosion leads to huge irreversible losses of metals; about 10% of the produced iron is completely destroyed every year. According to the Institute of Physical Chemistry of the Russian Academy of Sciences, every sixth blast furnace in Russia works in vain all the smelted metal turns into rust. The destruction of metal structures, agricultural and transport vehicles, and industrial equipment causes downtime, accidents, and deterioration in product quality. Taking into account possible corrosion leads to increased metal costs in the manufacture of high-pressure apparatus, steam boilers, metal containers for toxic and radioactive substances, etc. This increases overall corrosion losses. Considerable amounts of money have to be spent on anti-corrosion protection. The ratio of direct losses, indirect losses and costs for corrosion protection is estimated as (34):1:1. In industrial developed countries Corrosion damage reaches 4% of national income. In our country it amounts to billions of rubles a year.

Corrosion problems are constantly getting worse due to the continuous increase in metal production and the tightening of their operating conditions. The environment in which metal structures are used is becoming more and more aggressive, including due to its pollution. Metal products used in technology operate under conditions of increasingly high temperatures and pressures, powerful flows of gases and liquids. Therefore, the issues of protecting metal materials from corrosion are becoming increasingly relevant. It is impossible to completely prevent metal corrosion, so the only way to combat it is to find ways to slow it down.

The problem of protecting metals from corrosion arose almost at the very beginning of their use. People tried to protect metals from atmospheric influences with the help of fat, oils, and later by coating with other metals and, above all, low-melting tin (tinning). In the works of the ancient Greek historian Herodotus (5th century BC) and the ancient Roman scientist Pliny the Elder (1st century BC) there are already references to the use of tin to protect iron from rusting. Currently, the fight against corrosion is carried out in several directions at once: they are trying to change the environment in which a metal product operates, influence the corrosion resistance of the material itself, and prevent contact between the metal and aggressive substances of the external environment.

Corrosion can be completely prevented only in an inert environment, for example, in an argon atmosphere, but in the vast majority of cases it is impossible to actually create such an environment during the operation of structures and mechanisms. In practice, to reduce the corrosive activity of a medium, they try to remove the most reactive components from it, for example, they reduce the acidity of aqueous solutions and soils with which metals may come into contact. One of the methods of combating corrosion of iron and its alloys, copper, brass, zinc, and lead is the removal of oxygen and carbon dioxide from aqueous solutions. In the energy sector and some branches of technology, water is also freed from chlorides, which stimulate local corrosion. To reduce soil acidity, liming is carried out.

The aggressiveness of the atmosphere strongly depends on humidity. For any metal there is a certain critical relative humidity, below which it is not subject to atmospheric corrosion. For iron, copper, nickel, zinc it is 50-70%. Sometimes, to preserve items of historical value, their temperature is artificially maintained above the dew point. In closed spaces (for example, in packaging boxes), humidity is reduced using silica gel or other adsorbents. The aggressiveness of the industrial atmosphere is determined mainly by fuel combustion products ( cm. ENVIRONMENTAL POLLUTION). The prevention of acid rain and the elimination of harmful gas emissions help reduce losses from corrosion.

The destruction of metals in aqueous environments can be slowed down using corrosion inhibitors, which are added in small quantities (usually less than 1%) to aqueous solutions. They promote passivation of the metal surface, that is, the formation of a thin and dense film of oxides or other poorly soluble compounds, which prevents the destruction of the main substance. For this purpose, some sodium salts (carbonate, silicate, borate) and other compounds are used. If razor blades are immersed in a solution of potassium chromate, they will last much longer. Organic inhibitors are often used, which are more effective than inorganic ones.

One of the methods of corrosion protection is based on the development of new materials that have higher corrosion resistance. The search for substitutes for corrosive metals is ongoing. Plastics, ceramics, glass, rubber, asbestos and concrete are more resistant to environmental influences, but in many other properties they are inferior to metals, which still serve as the main structural materials.

Noble metals are practically resistant to corrosion, but they are too expensive for widespread use, so they are used only in the most critical parts, for example, for the manufacture of non-corrosive electrical contacts. Nickel, aluminum, copper, titanium and alloys based on them have high corrosion resistance. Their production is growing quite quickly, but even now the most accessible and widely used metal remains quickly rusting iron. Alloying is often used to impart corrosion resistance to iron-based alloys. This is how stainless steel is obtained, which, in addition to iron, contains chromium and nickel. The most common stainless steel in our time, grade 188 (18% chromium and 8% nickel), appeared in 1923. It is completely resistant to moisture and oxygen. The first tons of stainless steel in our country were smelted in 1924 in Zlatoust. Nowadays, many grades of steels have been developed that, in addition to chromium and nickel, contain manganese, molybdenum, tungsten and others chemical elements. Surface alloying of inexpensive iron alloys with zinc, aluminum, and chromium is often used.

To resist atmospheric corrosion, thin coatings of other metals that are more resistant to moisture and atmospheric oxygen are applied to steel products. Chromium and nickel platings are often used. Because chrome platings often contain cracks, they are usually applied over less decorative nickel platings. Protecting tin cans from corrosion by organic acids found in food products requires a significant amount of tin. Long time to cover kitchen utensils used cadmium, but it is now known that this metal is hazardous to health and cadmium coatings are used only in technology.

To slow down corrosion, varnishes and paints, mineral oils and lubricants are applied to the metal surface. Underground structures are covered with a thick layer of bitumen or polyethylene. The internal surfaces of steel pipes and tanks are protected with cheap cement coatings.

To make the paintwork more reliable, the metal surface is thoroughly cleaned of dirt and corrosion products and subjected to special treatment. For steel products, so-called rust converters containing orthophosphoric acid (H 3 PO 4) and its salts are used. They dissolve residual oxides and form a dense and durable film of phosphates, which can protect the surface of the product for some time. Then the metal is coated with a primer layer, which should adhere well to the surface and have protective properties (usually red lead or zinc chromate is used). Only after this can varnish or paint be applied.

One of the most effective methods of combating corrosion is electrochemical protection. To protect drilling platforms, welded metal bases, underground pipelines, they are connected as a cathode to external source current Auxiliary inert electrodes are used as an anode.

Another version of such protection is used for relatively small steel structures or additionally insulated metal objects (for example, pipelines). In this case, a protector is used - an anode made of a relatively active metal (usually magnesium, zinc, aluminum and their alloys), which gradually collapses, protecting the main object. With the help of one magnesium anode, up to 8 km of pipeline is protected. Tread protection is widespread; for example, in the USA, about 11.5 thousand tons of aluminum are spent annually on the production of protectors.

Protection of one metal by another, more active metal, located in the voltage series to the left, is effective without imposing a potential difference. More active metal(for example, zinc on the surface of iron) protects the less active metal from destruction.

Electrochemical methods of combating corrosion also include protection against destruction of structures by stray currents. One of the ways to eliminate such corrosion is to connect a metal conductor to the section of the structure from which the stray current flows with the rail along which the tram or electric train moves.

Elena Savinkina

LITERATURE Fremantle M. Chemistry in action. In 2 parts. M., Mir, 1991
Stepin B.D., Alikberova L.Yu. Chemistry book for home reading. M., Chemistry, 1994

Germans, French, Japanese - whose cars rust more? For how long do manufacturers today provide a guarantee against corrosion? What is cheaper – repair or warranty? Why is corrosion dangerous? There are a lot of questions.

Sooner or later everything rusts!

Corrosion, or the destruction of metal by natural chemical and electrochemical means, threatens almost every vehicle. It is not terrible only for plastic and high-quality stainless steel, undamaged by heat treatment (for example, welding).

Aluminum does not provide reliable protection, as it oxidizes over time, and insufficient insulation from steel leads to the formation of a galvanic couple. Audi services are well aware of this. The second generation A8 trunk lid was actively corroded in the area of the lining above the registration plate.

Corrosion – natural process, although some cars rust much more than others. For example, Skoda. Felicia of the second half of the 90s is “destroying” slowly, and the old Octavia is collapsing quickly. The decisive factors are both the quality of the source material and additional corrosion protection, as well as the design lines. Excessively complex profiles in risk areas, incorrect placement of drainage channels or even too high a welding current lead to the development of corrosion.

Rusty hell Mercedes.

Until now, many motorists evaluate the quality of a car depending on its country of origin. Premature corrosion of Lada and Dacia today does not surprise anyone, as does the long-term durability of the Volvo body. Corrosion of cars of Italian and French brands was considered standard in the eighties. Today, owners of “French” and “Italian” cars look down on cars of famous brands. In particular, PSA (Peugeot/Citroen) products have had better corrosion protection than VW cars since the beginning of the new millennium. While a 15-year-old Fiat Punto would only have a few warts, the old Mercedes E-Class was starting to look like metal.

Mercedes E-Class W210.

At one time, many Mercedes clients were lost forever. The A-class, S-class and Vito rusted equally quickly. Not so long ago, before 2006, the problem concerned the second generation A-Class (W169). The least resistant to corrosion was the E-Class W210 (1995-2003). The problem affected the C-Class W203 a little less frequently - until 2003. But in fact, any Mercedes produced before 2005 could bloom, even the new W211. The best way the seed was recommended by ML, which was collected in America.

Mercedes E-Class W210.

The Germans are rusting too.

Many without unnecessary words They consider German cars to be of high quality. However, they also rust quite often. For example, Ford Mondeo III (2000-2007), Ford Focus I and slightly smaller Focus II. The Opel Astra G is also an outsider: it’s not difficult to find leaky wheel arches and sometimes even the trunk lid. All the previous models of these brands are not even worth talking about.

Ford Focus II.

Old Volkswagen cars also suffered from corrosion. The situation improved significantly in 1997 with the arrival of the Passat B5 and Golf VI. But paradoxically, today in the Passat B6 2005-2010, small fires are sometimes found under the thin side door moldings. Not an epidemic, but still.

Only Audi and Porsche have demonstrated consistent quality since the mid-80s, with the exception of the Boxster. At that time, corrosion of the rear sills, rear wings and trunk lid was quite common in BMW cars. Even relatively young BMWs have 3 E46 (1998-2005), 5 E39 (1995-2003). Later models do not yet show such ailments.

Asian brands.

Corrosion is considered common among Japanese branded vehicles up until about 2002. Toyota and Lexus models have proven themselves to be the most stable. Corrosion of the sills in the Toyota Urban Cruiser is only occasionally detected.

Honda got better after 2003 (Accord, Legend and 2nd generation CR-V). In the case of the Civic, significant corrosion existed only on the Civic 6G model (until 2001). In the seventh generation Civic, pinpoint outbreaks were only occasionally detected.

The Nissan Almera N16 (2000-2006) was a huge disappointment. Young Mazda models were also surprising. In addition to the elderly MX-5 roadster, which is used primarily in dry weather, corrosion attacked the first generation Mazda 3 and Mazda 6 (2002-2007). In all three of these models, the edges of the rear wings began to bloom after a few years.

Mazda MX-5.

For Korean car brands, the situation is a little better than is usually believed. “Rusty pieces” remained in the mid-90s. Later models have only minor problems. For example, the first generation of Hyundai i30 and Kia Ceed: corrosion of the edges of the rear doors and trunk door, glass frames.

SUVs rust more often.

SUVs are at risk. The reasons are obvious - abrasions after contact with various items and overcoming mud and water. The most famous example is the Suzuki Jimny. The exterior body panels will withstand anything during the six-year warranty period. But the chassis, frame and vacuum tubes connecting the front axle can change beyond recognition. The situation with the Mitsubishi Pajero III (2000-2006) is only slightly better. Of the Korean SUVs, the first generation Kia Sorento (2002-2009) suffers most often. In his case, the accumulation of dirt and water under the plastic trims and poor protection along the edges of the doors are to blame.

Suzuki Jimny.

Guarantee – protection or trick?

The manufacturer's warranty against through corrosion does not reflect the actual quality of anti-corrosion protection. In addition, it would be necessary to clarify what the manufacturer’s guarantee is for. A real guarantee implies protection “against through corrosion from the inside,” i.e. no corrosion underneath original paint, undamaged as a result of an accident or exposure to an aggressive environment.

In addition, the warranty usually covers sills, fenders, doors, hood, etc., i.e. for local parts that will not require large financial costs and a lot of time for dismantling and restoration. Only some manufacturers are ready to make an exception. For example, Jeep explicitly states that it will only cover the cost of repair and replacement of any rusted items if the corrosion is not caused by external damage.

Mercedes is ready to provide a long-term guarantee of corrosion protection only if the car is serviced at an official service center throughout the entire period.

Mercedes Vito.

What is cheaper: a long warranty or repairs at your own expense?

Most brands, like Mercedes, are ready to replace a rusty wing on a car older than 10 years at their own expense only if you patiently pay the maintenance bills at the official service center every year.

But there are a few caveats. Firstly, not all dealers will be ready to recognize corrosion of an old car as a manufacturing defect. Secondly, repairing a small defect is much cheaper than going to the “officials” for maintenance every year.

Mitsubishi Pajero 2000-2006.

Prevention.

Many motorists have repeatedly noticed an interesting paradox. Cars stored in a garage have better paintwork than those parked outside. But it is garage cars that often bloom faster. Poorly ventilated garages contribute to this. In winter, salty slush remains inside all kinds of body cracks and niches. A warm engine heats the air, creating favorable conditions for the destructive effects of salt. Parking outside in the sun and wind is the cheapest and easiest way to prevent corrosion.

Today there are a large number of means to protect the body, both outside and inside. Many services are ready to perform labor-intensive and time-consuming anti-corrosion protection procedures, but not always with good quality.

Dacia Logan.

Guaranteed against through corrosion.

Currently, manufacturers guarantee the following periods against through corrosion.

Alfa Romeo - 8 years
Audi - 12 years
BMW - 12 years
Citroën - 12 years (Combi-passenger models - 6 years)
Chevrolet - 6 years
Chrysler - 8 years
Dacia - 6 years old
Fiat - 8 years
Ford - 12 years (Ka - 8 years)
Honda - 12 years
Hyundai - 12 years
Jaguar - 6 years
Jeep - 7 years
Kia - 12 years old
Lancia - 8 years
Land Rover - 6 years
Lada - 3 years (Niva) or 6 years (others)
Mazda - 12 years (BT-50 - 6 years)
Mercedes-Benz - 30 years
Mini - 12 years
Mitsubishi - 12 years
Nissan - 12 years
Opel - 12 years
Peugeot - 12 years (Combi-passenger models - 6 years)
Renault - 12 years (Master - 6 years)
Seat - 12 years
Subaru - 12 years
Suzuki - 12 years (Jimny - 6 years)
Skoda - 12 years
Toyota - 12 years
Volkswagen - 12 years
Volvo - 12 years (1st generation XC90 8 years)

Many materials, such as metal, ceramic, and wood, are susceptible to corrosion as a result of exposure to them. As a rule, this effect is achieved due to the instability of the structure, which is affected by the thermodynamics of the environment. In this article we will look in detail at what metal corrosion is, what types it has, and how you can protect yourself from it.

Some general information

The word “rust” is quite popular among people, which refers to the process of corrosion of metal and various alloys. People use the term “aging” for polymers. In fact, these words are synonyms. A striking example is the aging of rubber products that actively interact with oxygen. Some plastic products can quickly become unusable due to precipitation. How quickly the corrosion process occurs depends entirely on the conditions in which the product is placed. Ambient humidity is especially affected. The higher its indicator, the faster the metal will become unusable. Scientists have experimentally found that about 10% of products in production are simply written off due to corrosion. The types of this process are different, their classification depends on the type of environment in which the products are located, the speed and nature of the process. Next, let's look at the types of corrosion in more detail. Now every person should understand what metal corrosion is.

Artificial aging

The corrosion process does not always have a destructive effect and renders certain materials unusable. Often, due to corrosion, the coating acquires additional properties necessary for humans. That's why it became popular artificial aging. It is most often used when it comes to aluminum and titanium. Only through corrosion can increased strength of materials be achieved. In order to complete the destruction process correctly, it is necessary to use heat treatment. Considering that the natural aging of materials under some conditions is a rather slow process, there is no need to specify that when using this method the material must have a special hardening. You must also understand all the risks associated with this method. For example, although the strength of the material increases, its ductility decreases as much as possible. With ease, the reader can now answer the question of what artificial metal corrosion is.

Reviews about heat treatment

This method compacts the molecules of the material, and the structure changes accordingly. Often thermal protection is necessary to strengthen pipelines, as it helps protect the material from rust, as well as minimize the pressure that is exerted on the structure if it is located underground. Users of this technique leave reviews in which they describe that this method of protection is as effective as possible and really shows good results. It is advisable to use this treatment only in the industrial sector. Due to the fact that chambers for firing and other processes necessary to obtain reliable protection are expensive, the method is not popular. This protection of metal from corrosion is quite effective.

Classification

At the moment there are more than 20 rusting options. This article will describe only the most popular types of corrosion. Conventionally, they are divided into the following groups, which will help you understand in more detail what metal corrosion is.

Chemical corrosion is interaction with a corrosive environment. In this case, the oxidation of the metal and the reduction of the oxidizing agent occur simultaneously in one cycle. Both materials are not separated by space. Let's look at other types of metal corrosion.

Electrochemical corrosion is the interaction of a metal with an electrolyte. The atoms are ionized, the oxidizing agent is reduced, and these two processes occur in several cycles. Their speed depends entirely on the potential of the electrodes.

With gas corrosion, metal with a small liquid content rusts. Moisture should not exceed 0.1%. Also, this type of corrosion can occur in a gas environment at high temperatures. This species is most often found in the chemical and oil refining industries.

In addition to those described above, there are many other types of corrosion of materials. There are biological, targeted, contact, local and other types of rust.

Electrochemical corrosion and its features

With electrochemical corrosion, the destruction of the material occurs due to its contact with the electrolyte. The last substance may be condensate or rainwater. It should be noted that the more salts there are in the liquid, the higher the electrical conductivity. Accordingly, the corrosion process will proceed quite quickly. If we talk about the most popular places that are susceptible to corrosion, we should note rivets in a metal structure, welded joints, as well as simply places where the material is damaged. It happens that when an iron alloy is created, it is coated with special substances that have anti-corrosion properties. However, this does not prevent the rusting process, but only slows it down. A fairly striking example is galvanizing. Zinc has a negative potential when compared to iron. Because of this, the latter material will be restored, and the zinc will be damaged. If there is an oxide film on the surface, the destruction process will take a long time. Electrochemical corrosion has several types, but it should be noted that they are all dangerous and, as a rule, it is impossible to stop this type of metal corrosion.

Chemical corrosion

Chemical corrosion is quite common. For example, if a person notices scale, then he must understand that it appeared as a result of the combination of metal, that is, interaction, with oxygen. As a rule, if the ambient temperature is high, the corrosion process will be noticeably accelerated. Liquids can participate in rusting, that is, water, salt, any acid or alkali, salt solutions. When it comes to chemical corrosion of metals such as copper or zinc, their oxidation leads to a persistent film corrosion process. The rest form iron oxide. Further, all the chemical processes that will occur will lead to the appearance of rust. It will not provide protection in any way, but rather promotes corrosion. Galvanizing can currently protect many materials. Other means of protection against chemical corrosion of metals have also been developed.

Types of concrete corrosion

Brittleness of concrete can be caused by one of three types of corrosion. Quite often there is a change in structure of this material. Let's look at why this happens.

The most common type of corrosion is the destruction of cement stone. As a rule, this occurs when liquid and precipitation constantly affect the material. Because of this, the structure of the material is destroyed. Below are more detailed examples of metal corrosion:

Interaction with acids. If the cement stone is constantly exposed to these materials, a rather aggressive element will be formed that is harmful to the coating. We are talking about calcium bicarbonate.
Crystallization of sparingly soluble substances. We are talking about corrosion here. Due to the fact that fungi, spores and other substances enter the pores, the concrete coating begins to quickly deteriorate.

Corrosion: methods of protection

Due to corrosion, manufacturers often suffer huge losses, so a lot of work is being done to avoid this process. Moreover, it should be noted that most often it is not the metal itself that is susceptible to corrosion, but huge metal structures. Manufacturers spend a lot of money on their creation. Unfortunately, it is almost impossible to provide 100% protection. However, if you properly protect the surface, that is, carry out abrasive blasting, you can delay the corrosion process for several years. They also combat it with paint and varnish. It reliably protects the material. If the metal is underground, it must be treated with special materials. This is the only way to achieve maximum metal protection from corrosion.

Anti-aging measures

As mentioned above, the corrosion process cannot be stopped. But you can maximize the time during which the material will degrade. Also, in production, as a rule, they try to get rid of factors that affect the aging process as much as possible. For example, in factories, each structure is periodically treated with solutions and polishes. They relieve the material from the negative impact on the metal from mechanical, temperature and chemical conditions. In order to understand this in more detail, you should study the definition of metal corrosion. If we talk about slowing down the aging effect, it should be noted that heat treatment can be used for this. Under normal operating conditions, this method will minimize the rapid destruction of the material. To ensure that the seams on the product do not come apart, welders use firing at a temperature of 650 degrees. This technique will reduce the intensity of aging.

Active and passive methods of control

Active methods of combating corrosion work by changing the structure of the electric field. To do this, you need to use direct current. The voltage must be such that the product has improved characteristics. A fairly popular method would be to use a “sacrificial” anode. It protects the material through its own destruction. The conditions for metal corrosion are described above.

As for passive protection, a paint coating is used for this. It completely protects the product from liquids and oxygen. Thanks to this, the surface is maximally protected from destruction. Sputtering of zinc, copper, and nickel should be used. Even if the layer is severely damaged, it will still protect the metal from rust. Of course, you need to understand that passive protection methods will only be relevant if the surface does not have cracks or chips.

Reviews about paint and varnish protection of metals

At the moment, paint protection is particularly popular. It is effective, flexible in use, and inexpensive. However, if long-term use of a metal structure is necessary, then this method of protection will not work. Paint and varnish coatings will not be able to protect the material for more than 7-8 years. Accordingly, they will have to be updated. Most likely, you will have to carry out restoration and replace the surface of the material. Other disadvantages of this coating include limitations in terms of use. If it is necessary to strengthen pipes that are located underground or under water, then paint protection will not work. Therefore, it should be understood that if it is necessary for the structure to be used for more than 10 years, other methods of protection should be resorted to.

Galvanizing in detail

Having considered the main types of corrosion, it is also necessary to discuss the most effective methods protection. One of these can be called galvanizing. It allows you to protect the material from severe damage by changing physical and chemical properties. At the moment, this method is considered economical and effective, given that almost 40% of all mined material on Earth is spent on zinc processing. It is important to treat the material with an anti-corrosion coating.

Galvanizing is carried out for steel sheets, fasteners, appliances and large metal structures. In general, using this type of spraying you can protect products of any size and shape. Zinc has no decorative purpose, although occasionally it can be added to the alloy to produce shine. In general, you need to understand that this metal will provide maximum protection against corrosion even in the most aggressive conditions.

Features of rust protective agents

When working with metal, any person understands that before applying protective materials, it is necessary to prepare the surface. Often all the difficulties lie precisely in this stage. In order to create a special barrier that will allow rust to reach the metal, it is necessary to introduce the concept of a compound. Thanks to it, the kit will provide protection against corrosion. In this case, electrical insulation takes place. It is usually quite difficult to protect against corrosion of ferrous metals.

Due to the specific nature of the use of various protective agents, it is necessary to understand the operating conditions of the material. If the metal will be located underground, then it is necessary to use multilayer coatings that will have not only anti-corrosion properties, but also enhanced protection from mechanical damage. If we are talking about communications that actively interact with oxygen and gases, you should use a product that minimizes the effect of water and oxygen. Accordingly, increased attention from the manufacturer will be paid to insulation from moisture, steam and low temperatures. In this case, additives and special plasticizers should be added, because the causes of metal corrosion are different and should be protected from all types.

Mixture "Urizol"

The Urizol mixture should be considered separately, as it is used to coat the pipeline. It is also suitable for fittings, connecting parts, valve units and those products that are constantly in contact with oil or gases. This composition is needed in order to get rid of the influence of underground and atmospheric influences. Often this mixture is also used to insulate concrete materials. This substance is applied very simply, without any difficulty. In order to treat the surface, you must use a sprayer. This is the only way to avoid corrosion of metals and alloys of similar products. As soon as the components combine, the reaction begins. Because of this, polyurea occurs. After this, the mixture turns into a gel-like and non-flowing state, and after some time it becomes solid. If the polymerization rate is slow, smudges will begin to form. They are harmful because they make it difficult to increase the thickness of the coating. It should be noted that this mixture for a long time maintains a sticky state. Due to this, all layers will be as uniform as possible, and intermediate thickness measurements will be equal to each other. If the polymerization process is too fast, the adhesion of the composition will decrease. In this case, the thickness of the resulting insulation layer will be uneven. By the way, the spray gun quickly becomes clogged if the coating speed is too fast. Metal corrosion factors will not appear if everything is done correctly. In order to prevent such situations, it is necessary to carefully select components and follow manufacturing rules.

Paints and enamels

Metal-plastic structures can be protected using three methods.

Paint coatings have already been described. They are simple, come in a variety of colors, and can be used to easily process large surfaces. Since the process of metal corrosion is quite fast, you should immediately think about coating with materials.

The second type is plastic coverings. As a rule, they are made of nylon and PVC. This coating will provide maximum protection against water, acids and alkalis.

The third type is rubber coating. It is often used to protect tanks and other structures from the inside.

Phosphating and chromating

The metal surface must be properly prepared for the protection process. Which methods will be used depends entirely on the type of surface. For example, ferrous metals are protected by phosphating. Non-ferrous metals can be processed using both methods. In general, if we talk about chemical preparation, it is necessary to clarify that it takes place in several stages. To begin with, the surface is degreased. Then it is washed with water. Next, a conversion layer is applied. Afterwards it is washed again with two types of water: drinking and demineralized, respectively. Next, it remains to carry out passivation. Chemical treatment should be carried out using spray, immersion, steam and water jet methods. The first two methods must be used with the help of special units that will completely prepare the surface for work. Which method to choose depends on the size, configuration of the product, and so on. In order to better understand this issue, you should know the equations of metal corrosion reactions.

Conclusion

The article described what corrosion is and what types it has. Now any person after reading this article will be able to understand how to protect any material from aging. By and large, this is quite easy to do if you know all the necessary instructions. The main thing is to understand all the characteristics of the environment in which the material is used. If the products are located in a place where constant vibrations occur, and there are also severe loads, then cracks will appear in the paintwork. Because of this, moisture will enter the metal, and accordingly, the corrosion process begins immediately. In such cases, it is better to additionally use rubber sealants and gaskets, then the coating will last a little longer.

Additionally, it must be said that if the structure is prematurely deformed, it will quickly deteriorate and age. Accordingly, this can lead to completely unforeseen circumstances. This will cause material damage and may result in the death of a person. Accordingly, special attention should be paid to corrosion protection.