Stainless Steel Basics - Austenitic - Ferritic - Martensitic - Precipitation Hardening - Duplex

Steel, with moisture and oxygen forms rust. Rust that is porous and will continue to grow and flake until ultimately consuming all the steel.
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But if we add enough Chromium to steel, it has the effect of allowing only a thin layer of an oxide to form that does not allow the corrosion to continue. A “stain less” steel.

The degree of corrosion resistance depends on the amount of Chromium in the alloy and the effects of some other elements. Various compositions have been established as standard alloys.
So which alloy do we use?

Specific environment, temperature, strength required, fabricability, and ultimately... cost... are all involved in selecting which stainless steel is used in any given application.

Stainless steels are classified as Austenitic, Ferritic, Martensitic, Precipitation Hardening or Duplex based on their metallurgical structure.