(ASTM A 380) Preferred definition for the biopharmaceutical industry. - Removal of exogenous iron or iron compounds from the surface of a stainless steel by means of a chemical dissolution, most typically by a treatment with an acid solution that will remove the surface contamination but will not significantly affect the stainless steel itself. Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation.