To attain a contaminant free part, it may be necessary to add a pre-cleaning operation, e.g. vapor degreasing or alkaline cleaning. In the past, passivation was typically preceded by a pre-cleaning process known as “pickling”. The pickling solution, made from a hydrofluoric acid mixture, was used for dissolving embedded steel flecks and removing the heat tint and oxide scale. Due to EPA regulations, most companies have eliminated pickling. Without this aggressive pre-cleaning operation, in many cases, passivation does little to improve the corrosion resistance of stainless steels.