Oxides form naturally on stainless steel from many manufacturing processes such as soldering, welding, annealing and EDM to name a few. Pickling is the process of chemical removal of these oxides by means of a strong acid or base and is defined by ASTM A967 section 22.214.171.124 as "The chemical treatments capable of removing heat tint or oxide scale from stainless steel and capable of
dissolving the stainless steel itself". Metals such as Stainless Steel are considered passive after pickling but may be augmented by further treatments such as the Citric or Nitric baths or electro polishing. Materials such as copper and solders may also be pickled to produce a consistent surface finish, but materials such as these will eventually discolor with age as they oxidize.