Stainless Steel

Stainless steel is an alloy of iron which contains more than 10% chromium. One common element they all have is a certain minimum percentage (by mass) of chromium: 10.5%. Although other elements, particularly nickel and molybdenum, are added to improve corrosion resistance, the amount of chromium present greatly determines the corrosion resistance of steel.

CONSTITUENTS

The quality of stainless steel is imparted to steels by the presence of at least 12% of chromium in the steel. Oxidation and/ or corrosion produce a dense adherent oxide film which acts as a barrier to further corrosion.

Martensitic steel 13% chromium, and more than 0.1% carbon
Ferritic steel 13-17% chromium, and < 0.08% carbon
Austhentic steel Min 8% nickel, 17-24% chromium, max 0.1% carbon

References

Sinha Anil Kumar; Physical Metallurgy Handbook ; Mc.Graw Hill Inc; New York; 2003
Tisza, M; Physical Metallurgy for Engineers; ASM International and Freund Publishing House Ltd; Ohio; 2001