Passivation

Specification covers standard recommendation practice for cleaning and de-scaling stainless steel parts, equipment and systems. Cleaning includes all operations necessary for the removal of surface contaminants from metals to ensure:

(1) maximum corrosion resistance for the metal. 
(2) prevention of product contamination; and 
(3) achievement of desired appearance. (has no dimensional change)

Type I:     Low temperature 
Type II:   Medium temperature 
Type III:   High temperature 
Type IV:   For steels containing large amounts (0.15%)
of sulfur or selenium. 
Type V:    Anodic-for high carbon martensitic (440 steels). 
Type VI:   Low temperature (optional).