Passivation of steel

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Different types of steel have different anti-corrosion properties. Stainless steel, as a rule, does not corrode due to the fact that it usually has a passive layer that protects it from this phenomenon. However, the automatic passivation process does not apply to all types of metals, and what’s more, even a natural passive coating can be damaged by atmospheric and chemical factors. Then, in order to prevent the development of corrosion, it is necessary to carry out artificial passivation of steel.

Natural passive layer of steel

It protects the steel against corrosion. The passive layer may be the result of a natural process taking place spontaneously, without human intervention. It is a thin, transparent oxide layer that adheres tightly to the steel surface. It is created by a chemical reaction between the chromium contained in the steel and the oxygen present in the air. As a result, chromium oxide is produced as a protective coating.

Natural passivation does not apply to all types of metals and, moreover, sometimes the passive layer can become damaged. The most common reasons for this are grinding, welding, chemical reactions or heavy soiling. The damaged layer can rebuild itself – in the presence of oxygen – although sometimes its natural ability to rebuild disappears. This is mainly the case when steel is exposed to unfavourable environmental conditions associated with high moisture content or salinity. The corrosion process then begins on the unprotected surface.

In order to preserve the durability of the passive layer, it must be properly cared for by maintaining the surface of the material. In addition, it is a good idea to check the properties of a particular steel before executing the project and then select the right type to suit the environment. If damage to the passive layer occurs, it is necessary to passivate the steel again to ensure that it is protected from external agents.

What is passivation of steel?

In order to passivate steel, a specific section or all of the material must first be thoroughly cleaned of any discoloration or dirt. It is worth noting that properly conducted chemical passivation of steel results in an increase in the thickness of the protective layer by up to ten times. It is airtight and hard, and thus perfectly insulates the material from the threatening effects of the environment. Moreover, this process does not lead to any modification of the shape or structure of the surface. It only affects the anti-corrosion properties. Passivation of steel is often used, for example, after welding, which can result in the material losing its ability to restore its protective coating on its own.

Passivation of steel is the chemical or electrochemical protection of its surface. This is a process whereby oxide layers are artificially formed which are rich in chromium – as in natural conditions with sufficient oxygen. The resulting coating is highly resistant to the harmful effects of chemical and atmospheric agents. Thanks to the passive layer, oxidation of the steel is reduced and it therefore becomes corrosion resistant.

The surface of the steel should be smooth and free from any damage. The way it is finished also has a great influence on its resistance to the corrosion process. Please note that developing corrosion is a major safety hazard. In addition, damage to infrastructure can also result in serious financial losses. Therefore, the condition of the materials used should be checked systematically and reports should be made on any incidents that occur. In many cases, it is also necessary to passivate the steel, which is an effective solution for counteracting the dangerous phenomenon of corrosion.