Stainless steel is resistant to corrosion primarily due to the addition of chromium, which increases the passivation capacity of iron alloys. The transition to a passive state is marked by a sudden change in the electrochemical potential of the metal or alloy to a more positive value.

The phenomenon of metal passivation involves covering their surface with a very thin, tightly adhering and resistant layer of oxides, which protects the metal from corrosion. Passivation is a phenomenon that depends on the chemical composition of the alloy and the oxidation capacity of different environments. Iron and soft steel passivate, for example, in concentrated nitric acid and in solutions of strongly oxidizing compounds.

However, the passivation of iron is very unstable. On the other hand, some metals with a greater affinity for oxygen passivate more easily, and their passive state is much more durable.

One such metal is chromium, whose corrosion resistance is related to its ease of passivation. Chromium has the property of transferring its tendency to passivate to alloys with other metals. Iron alloys with chromium content above 13-14% Cr passivate under the influence of oxygen contained in the air. This ensures their chemical resistance, resulting in stainless steel.

The basic component of all stainless steels is therefore chromium, with a minimum content of 12%. In addition to chromium, nickel is often the second basic component of corrosion-resistant steels.

Corrosion-resistant chromium steels can be ferritic or martensitic, depending on their chromium and carbon content. In the case of martensitic steels, ferrite is completely transformed into austenite during heating. This makes it possible to harden the steel and form a martensitic structure. These steels harden during air cooling, which is why they are called martensitic.

The use of stainless steel

Stainless steel is a common type of steel. We encounter this type of steel in various places on a daily basis without even noticing it. When visiting a doctor, we can see that they use stainless steel tools because they are easy to disinfect, resistant to corrosion, and retain their sharpness and structural integrity despite intensive use. Due to its biocompatibility, it is used for implants. At home, we can find stainless steel in the kitchen, for example in stainless steel frying pans, pots, and kettles. Stainless steel is often used to make jewelry because it retains its aesthetic appearance for a very long time.

What are the costs of stainless steel?

The costs of stainless steel can vary depending on the type of steel and its application. In general, it is a more expensive material than ordinary carbon steel, but its durability and corrosion resistance make it a worthwhile investment in the long run.

Frequently asked questions
Is stainless steel magnetic?

Some types of stainless steel, such as ferritic and martensitic, are magnetic, while austenitic stainless steel is non-magnetic.

Why is stainless steel so popular?

Stainless steel is popular because of its corrosion resistance, durability, and aesthetics. It is a versatile material used in many industries.

How to care for stainless steel?

Stainless steel should be cleaned regularly, kept away from harsh chemicals, and polished periodically to maintain its aesthetic appearance. To keep it looking shiny, you can periodically polish it with special polishing compounds designed for this material.

Is stainless steel environmentally friendly?

Yes, stainless steel is fully recyclable and its production contributes to waste reduction and environmental protection.