What can cause corrosion

Causes of car corrosion

Corrosion is a physical and chemical process in which water and oxygen act on metal. The result of corrosion is the transition of metal into chemically stable oxides and salts. Rust is a product that results from corrosion. Almost all metal elements of a car have a tendency to corrode.

It appears most quickly in places where the paintwork is damaged (chips from stones, deep scratches to metal, etc.). A dirty car increases the risk of corrosion. Dirt and moisture form an electrolyte. As is known, in the presence of electrolytes, corrosion proceeds faster.

 This is especially true for the autumn-winter season of vehicle use.

Corrosion may appear in certain areas of the body in the form of spots (local corrosion). An example is contact corrosion, which occurs at the joints of parts (spot welding, bolts and rivets). The cracks and gaps of the car body, in which moisture accumulates and remains, are at high risk of corrosion.

Air humidity, as well as its pollution from exhaust and industrial gases, chemical products and dust, affect the rate of atmospheric corrosion. Thus, corrosion in industrial areas with high levels of air pollution can develop faster.

In addition to deteriorating the decorative properties of the paintwork, corrosion weakens the metal. It loses its strength, and when the power elements corrode, the safety of the body deteriorates.

Paintwork

The main protective barrier of metal from moisture and oxygen is the paint coating. It has the necessary anti-corrosion properties, such as water repellency, low gas and vapor permeability. Adhesion, thickness and integrity of the coating matter. Defects may occur during paint application and curing.

In the future, they will worsen the protective properties of the coating and increase permeability. The structure of the paint film itself may have pores. This is due to the structure, chemical composition of the molecules and their density. In general, any paint coating has pores. Their size is extremely small.

Also, the cause of paint porosity can be the evaporating solvent during curing, as well as the destruction of the structure of the paint film as a result of aging. An important parameter is the thickness of the paintwork. The coating must have a certain thickness.

If this parameter is reduced, the coating will have pores and the likelihood of corrosion increases. When applying paint and varnish, in order to maintain the required thickness, it is more correct to apply several thin layers instead of one thick one.

It must also be remembered that increasing the film thickness above the optimal parameters will lead to a deterioration in adhesive and protective properties. As soon as adhesion (sticking) is broken, there is immediately a danger of corrosion.

 Why does a painted surface rust?

As mentioned above, paint and varnish coatings cannot be called completely impenetrable. They have low permeability to moisture and oxygen, but still have. Staying in a humid environment for too long will inevitably start the corrosion process.

An important factor in the occurrence of corrosion is exposure to an aggressive environment. Temperature changes, high humidity and polluted air, solar radiation, all this affects the paint and ages it. In addition, while driving at speed, small and large solid particles fly from the road onto the body, which gradually damage the paint.

The appearance and development of corrosion is influenced by where the vehicle is stored. The car must be stored in a dry, ventilated area. But, for example, if you choose between outdoor storage and an unventilated, damp garage, it is better to choose the first option.

Sand-salt mixture on roads

In areas where low winter temperatures cause salt-containing compounds to be applied to slippery roads. This is a mixture of industrial salt and sand, which is designed to prevent ice and act on already icy roads. Sand helps prevent salt from scattering and spreading, and also reduces slipping on the road.

As a result of the action of this mixture, a “porridge” of salt and melted snow is obtained. All this has an aggressive effect on the protective coating of the body, and especially on places that have microdamages to this coating. In areas where roads are sprinkled with a sand-salt mixture, individual parts of the car, without timely care and treatment, rust quite quickly.

Rust converters

Rust converters are necessary to combat corrosion. They contain orthophosphoric acid and other additives that act on rust, stop its spread and form a protective layer from it.

In essence, rust becomes an inert compound that has no effect on the metal. It is very important to remove loose rust before applying the converter.

Only a minimal amount of rust should remain that cannot be removed with tools.

There are also converting soils. They transform rust and prepare the surface for the next layer of the required coating.

How to prevent corrosion?

It is better to prevent the occurrence of corrosion, since it is quite difficult to combat it. In most cases, you have to cut out the rusted areas and weld in repair inserts, or replace the entire panel. You can read the article “how to remove rust from a car” about ways to remove rust.

Regular care of your car's paintwork and timely restoration of anti-gravel and anti-corrosion coatings will help extend the life of the body and prevent corrosion.

So, we can give the following recommendations and advice:

• Wash your car every two weeks or once a week, especially during the icy season, when there is slush and salt on the roads.
• Don't forget to wash the areas under the car and wheel arches at least once a week.
• Try to quickly repair paint damage. If signs of corrosion appear, remove them immediately. If you have time to cover the chip with repair paint before corrosion appears, this will prevent its occurrence. If rust begins to appear in the chip, you need to clean it off with sandpaper (you can use abrasive size P220 or finer), degrease it and cover it (cover it with a brush) with body-colored repair paint.
• Apply a wax protective layer. Proper application of wax will increase the body's corrosion resistance and also provide protection from damage. Waxes or special synthetic protective sealants will fill the pores and cracks of the paintwork, forming a film.
• The bottom and arches should be covered with anti-corrosion agent as necessary.
• Most detergents remove the protective wax from the body. We must remember to periodically restore the protective coating of the body.
• If your car is covered in salt before washing, add baking soda to the water to neutralize the salt.

Note: It must be remembered that any protective coatings must be applied to a thoroughly cleaned, degreased and dried surface. Protective coatings applied incorrectly can damage the paintwork and only accelerate the onset of corrosion.

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Source: https://kuzov.info/prichini-korrozii-avtomobila/

Metal corrosion

Corrosion - destruction of the surface of steels and alloys under the influence of various physical and chemical factors - causes enormous damage to parts and metal structures. Every year this invisible enemy “eats” about 13 million tons of metal. For comparison, the metallurgical industry of the European Union countries produced only 0.5 million tons more in 2014. And these are just direct losses. And long-term operation of steel products without their effective protection against corrosion is generally impossible.

What is corrosion and its types

The main reason for intense oxidation of the surface of metals (which is the main cause of corrosion) are:

1. Increased environmental humidity.
2. Presence of stray currents.
3. Unfavorable atmospheric composition.

Accordingly, the chemical, tribochemical and electrochemical nature of corrosion is distinguished. It is they, in the totality of their influence, that destroy the bulk of the metal.

Chemical corrosion

This type of corrosion is caused by active oxidation of the metal surface in a humid environment. The undisputed leader here is steel (excluding stainless steel). Iron, being the main component of steel, when interacting with oxygen forms three types of oxides: FeO, Fe2O3 and Fe3O4.

The main trouble is that the oxide corresponds to a certain range of external temperatures, so practical protection of steel from corrosion is observed only at temperatures above 10000C, when a thick film of high-temperature oxide FeO itself begins to protect the metal from subsequent rust formation.

This process is called bluing, and is actively used in technology to protect the surface of steel products. But this is a special case, and in most cases it is impossible to actively protect the metal from corrosion in this way.

Chemical corrosion is activated at elevated temperatures. The tendency of metals to chemical oxidation is determined by the value of their oxygen potential - the ability to participate in redox reactions. Steel is not the worst option: lead, cobalt, and nickel, in particular, oxidize more intensely.

Electrochemical corrosion

This type of corrosion is more insidious: the destruction of the metal in this case occurs due to the combined influence of water and soil on the steel surface (for example, underground pipelines).

Wet soil, being a slightly alkaline environment, promotes the formation and movement of stray electrical currents in the soil. They are a consequence of the ionization of metal particles in an oxygen-containing environment, and initiates the transfer of metal cations from the surface to the outside.

The fight against such corrosion is complicated by the difficulty of diagnosing the condition of the soil at the site of laying steel communications.

Electrochemical corrosion occurs when the contact devices of power lines oxidize when the gaps between the elements of the electrical circuit increase. In addition to their destruction, in this case the power consumption of devices increases sharply.

Tribochemical corrosion

Metalworking tools that operate at elevated temperatures and pressures are susceptible to this type. Anti-corrosion coating of cutters, punches, dies, etc. is impossible, since the part requires high surface hardness.

Meanwhile, during high-speed cutting, cold pressing and other energy-intensive metal processing processes, mechanochemical reactions begin to occur, the intensity of which increases with increasing temperature at the “tool-workpiece” contact surface.

The resulting iron oxide Fe2O3 is characterized by increased hardness, and therefore begins to intensively destroy the surface of the tool.

Corrosion control methods

The choice of an appropriate method for protecting the surface from rust formation is determined by the conditions in which the part or structure operates. The following methods are most effective:

• Application of surface weather-resistant coatings;
• Surface metallization;
• Alloying the metal with elements that are more resistant to participation in redox reactions;
• Changes in the chemical composition of the environment.

Mechanical Surface Coatings

Surface protection of metal can be done by painting it or applying surface films that are neutral in composition to the effects of oxygen. In everyday life, as well as when processing relatively large areas (mainly underground pipelines), painting is used.

Among the most durable paints are enamels and paints containing aluminum.

In the first case, the effect is achieved by blocking access to oxygen to the steel surface, and in the second, by applying aluminum to the surface, which, being a chemically inert metal, protects the steel from corrosion destruction.

The positive features of this method of protection are the ease of its implementation and relatively low financial costs, since the process is quite simply mechanized. At the same time, the durability of this method of protection is low, since, not having a high degree of affinity with the base metal, such coatings begin to mechanically deteriorate after some time.

Chemical surface coatings 

Corrosion protection in this case occurs due to the formation on the surface of the metal being processed of a chemical film consisting of components that are resistant to oxygen, pressure, temperature and humidity. For example, carbon steels are treated with phosphating.

The process can be performed either cold or hot, and consists of forming a layer of manganese and zinc phosphate salts on the metal surface. An analogue of phosphating is oxalation - the process of treating metal with oxalic acid salts.

   The use of precisely such technologies increases the resistance of metals against tribochemical corrosion.

The disadvantage of these methods is the labor intensity and complexity of their application, which requires special equipment. In addition, the final surface changes its color, which is not always acceptable for aesthetic reasons.

Alloying and metallization

Unlike previous methods, here the end result is the formation of a layer of metal that is chemically inert to oxygen. These metals include those that are as far as possible from hydrogen on the oxygen activity line. As efficiency increases, this series looks like this: chromium→copper→zinc→silver→aluminum→platinum.

The difference in the technologies for obtaining such anti-corrosion layers lies in the method of their application.

During metallization, an ionized arc flow of finely dispersed sprayed metal is directed to the surface, and alloying is carried out during the process of metal smelting, as a consequence of the occurrence of metallurgical reactions between the base metal and the introduced alloying additives.

Changes in the composition of the environment

In some cases, a significant reduction in corrosion can be achieved by changing the composition of the atmosphere in which the protected metal structure operates. This can be evacuation (for relatively small objects), or work in an environment of inert gases (argon, neon, xenon).

This method is very effective, but requires additional equipment - protective chambers, suits for operating personnel, etc.

It is used mainly in research laboratories and pilot production, where the necessary microclimate is specially maintained.

Whoever hinders us will help us

In conclusion, we will point out a rather unusual method of corrosion protection: with the help of iron oxides themselves, more precisely, one of them - iron oxide Fe3O4. This substance is formed at temperatures of 2505000C and, in terms of its mechanical properties, is a highly viscous technological lubricant.

Being present on the surface of the workpiece, Fe3O4 blocks access to air oxygen during semi-hot deformation of metals and alloys, and thereby blocks the process of initiation of tribochemical corrosion. This phenomenon is used for high-speed upsetting of hard-to-deform metals and alloys.

The effectiveness of this method is due to the fact that with each technological cycle the contact surfaces are renewed, and therefore the stability of the process is adjusted automatically.⁠

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Difference between corrosion and rust

Corrosion and rust are two different terms that express the same idea. Corrosion is a type of oxidation. Rust is a type of corrosion. Corrosion can occur on metal surfaces as well as non-metallic surfaces. Corrosion can be caused by exposure to air and moisture or by the spread of chemicals on surfaces.

Rust is the chemical process of forming a red-orange coating on the surface of iron or steel. This is oxidation.

The main difference between corrosion and rust is that corrosion can occur due to chemicals, whereas rust does not occur due to chemicals, although it can be accelerated by certain chemicals.

Key areas covered

1. What is corrosion
- definition, process, causes, prevention
2. What is rust
- definition, process, prevention
3. What is the difference between corrosion and rust
- Comparison of the main differences

Key words: acid, base, chromium, corrosion, electroplating, galvanization, iron, oxidation, rust, steel

What is corrosion

Corrosion is the process of destruction of a substance as a result of chemical, electrochemical or other reactions that occur on the surface of this substance. Corrosion can occur on both metallic and non-metallic surfaces. Corrosion of a material affects the surface structure of the material. The most common example of corrosion is rust. Here the color and quality of the steel changes.

Corrosion can also occur on non-metallic surfaces such as countertops and leather. When certain harsh chemicals fall on these surfaces, deterioration of that surface can occur.

Such chemicals include strong acids and strong bases; for example, acids like HCl, H2TAK4 and bases like NaOH, KOH, etc. Chemicals that cause corrosion are known as corrosive chemicals.

These chemicals can cause visible deterioration of surfaces that is permanent damage. The surface can be skin, eye, wood, metal, etc.

Figure 1: Chemicals should be handled with care.

The following actions can reduce corrosion,

• Surface painting
• galvanization
• Handle chemicals carefully

What is rust

Rust is a red or orange coating that forms on the surface of iron when exposed to air and moisture. This is a type of corrosion. This is caused by a chemical reaction between the surface of the metal and the moisture and oxygen in the air.

The most common substances that corrode are iron and steel. Rust does not occur due to chemical spills.

But some chemicals can speed up rusting by increasing electrical activity between iron and oxygen.

Figure 2: Rust on chains

Rust on iron or steel is also known as metal oxidation. This is because metal atoms on the surface are oxidized by oxygen in the air in the presence of water. For example, Fe+2 in steel can be oxidized to Fe+3 during iron corrosion. The rate of corrosion depends on several factors such as air humidity, metal surface area that is exposed to air, etc.

There are several methods to prevent metals from rusting. Some of these strategies are listed below.

• Environmental modifications
• Galvanization - Zinc coating can prevent iron from rusting by acting as a sacrificial anode.
• Corrosion inhibitors are chemicals that can prevent rust from forming by interrupting the oxidation reaction on the metal surface.
• Paints. Coating with paints helps prevent rust.
• Electroplating is a process where a thin layer of metal (eg nickel, chromium) is applied to the surface of steel.

However, stainless steel is an exception because it does not rust. This is due to the presence of chromium (10-20%) as a component. Chromium can form a thin film by reacting with oxygen in air and water. This thin film prevents stainless steel from rusting.

Definition

Corrosion: Corrosion is the process of destruction of a substance as a result of chemical, electrochemical or other reactions that occur on the surface of that substance.

Rust: Rust is a red or orange coating that forms on the surface of iron when exposed to air and moisture.

surface

Corrosion: Corrosion can occur on different surfaces such as leather, wood, metals, etc.

Rust: Rust mainly occurs on iron and steel surfaces.

causes

Corrosion: Corrosion can occur due to exposure to air or the spread of chemicals on surfaces.

Rust: Rust can occur due to exposure to air and moisture.

Examples

Corrosion: Corrosion can occur in the form of skin burns, wood surface deterioration, or rust.

Rust: Rust can be observed as a red or orange coating on the surface.

Conclusion

Corrosion is a type of oxidation. Rust is a type of corrosion. The main difference between corrosion and rust is that corrosion can occur due to chemicals, whereas rust does not occur due to chemicals, but can be accelerated by certain chemicals.

Recommendations:

1. “What is corrosion? Corruptia,

Source: https://ru.strephonsays.com/difference-between-corrosion-and-rusting

Can rust be good for you?

Metal objects are very strong and durable, easy to use. However, they have a significant drawback: they are susceptible to rust.

Our editors decided to study the question - can rust be useful? Or it only causes harm to metal products.

You can find answers to any questions on the Internet if you try hard enough. Now let's look at what methods of protecting metal from rust exist.

How to protect metal products from corrosion

The process of metal corrosion is a chemical reaction of the alloy to the external environment. This problem can only be eliminated chemically.

Modern protection of metal structures from corrosion is based on the following:

• We increase the chemical resistance of products

• We isolate the metal surface from the aggressive environment

• We reduce the dangerous influence of the external environment

• Electrochemical protection - reducing corrosion by applying current

• Converting rust into a protective layer.

The last method is more suitable for solving our issue. The editors decided to conduct an experiment to restore a metal product from rust.

How rust can be beneficial

Probably, in every home you can find various metal products. These can be decorative ornaments, garden tools, and various household items. After tidying up your country attic or garage, you can find a lot of old, unused things.

One of our employees had an old metal tray left over from his grandmother for a long time. It was decided to give it a second life. It had long since lost its aesthetic appearance; the paint on it was badly cracked in places, peeling off, and rust was visible through it. He was just perfect for conducting the experiment.

After reading on the Internet, a new tool was found that should help answer our question. This is the chemical gel PreoCorr. According to the manufacturer, it is designed specifically to convert iron oxide into a durable protective layer with improved properties. The gel is very easy to use and safe if the safety regulations are strictly followed.

All procedures for preparing the surface for painting a metal tray were carried out according to the instructions.

1. wash the tray from dust and dirt
2. clean the surface of old paint using a special metal paint remover
3. apply preocor to the entire surface
4. wait until the product dries completely for 15 minutes
5. check the color of the treated surface, it should be a uniform whitish shade, without traces of rust.
6. coat the tray with new paint.

After the experiment, the tray turned out like new, and now it can be used in the household.

As a result of the experience, we received an answer to the main question. Surface rust can be beneficial if its properties are used correctly. In our case, testing Preocor on a metal tray showed that the chemical reaction of the rust helped create an improved protective layer on the surface of the tray.

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Source: https://erciem.ru/help/articles/provereno-na-praktike/mozhet-li-rzhavchina-byt-poleznoy.html