Why does chromium prevent rust

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All Rights Reserved. Summary Close iron will corrode when exposed to the atmosphere stainless steel resists corrosion the chromium in stainless steel forms a very thin protective oxide layer. The nature of corrosion. The combination of iron with oxygen in moist conditions is an energetically favourable process. We find it as iron oxide in an iron ore. In order to free the iron from its oxide we have to supply energy in a Blast Furnace see The chemistry of steelmaking.

The iron we extract tends to re-form its oxide in an electrochemical process we call corrosion. Rust compromises the mechanical characteristics of metal, alters the chemical properties, and is usually not considered aesthetically pleasing. It is for these reasons that many people in charge of design and material selection try to avoid having to deal with rust and the negative effects that come with it.

Aluminum cannot rust. This is because of the fact that rust is iron oxide, and most aluminum has virtually no iron in its composition. However, aluminum does oxidize, but it actually protects the underlying unoxidized aluminum. This is because the aluminum oxide is more corrosion resistant than the aluminum alloy it rests on. This is different than rust, because rust will flake away from an iron alloy thus allowing the rusting process to continue until material failure. Stainless steel is another example of a metal that does not rust.

Through it is important to note that some grades are more resistant to rust than others. Austenitic stainless steels such as or have high amounts of nickel and chromium. The chromium combines with the oxygen before the iron is able to which forms a chromium oxide layer.

This layer is very corrosion resistant which prevents rust formation and protects the underlying metal.