STAINLESS STEEL

Stainless steel is defined as a steel alloy having a minimum of 10.5% to 11% chromium content by mass. This chromium content means stainless steel does not corrode, rust or stain within water as ordinary steels do. It is the addition of chromium that differs Stainless steel from carbon steel. Unprotected carbon steel rusts readily when exposed to air and moisture forming an iron oxide film (rust) on the surface which is active and accelerates corrosion by forming more iron oxide if continually exposed to this type of atmosphere, this is due to the dissimilar size of the iron and iron oxide molecules (iron oxide is larger), the iron tends to flake and fall away. Exposed to the same conditions Stainless steels contain sufficient chromium to form a passive film of chromium oxide on the surface which prevents further corrosion and blocks corrosion from spreading into the metal's internal structure, due to the similar size of the steel and oxide molecules they bond very strongly and remain attached to the surface.