Definitions for "Passivating"
Passivating is the process of dissolving ferrous particles and surface impurities from stainless steel by chemical means (normally a nitric acid dip) and to produce a passive film on the surface. The purpose is to improve the corrosion resistance of the surface. Physical Properties: Physical properties are the properties defining the basic characteristics of the material or fastener, They are inherent in the raw material and remain basically unchanged in the fastener following its manufacture and include: density, coefficient of thermal expansion, electrical conductivity, thermal conductivity and magnetic properties.
A very confusing term, since the common usage has taken on a different meaning than the technical definition. Technically, passivation is not cleaning but is a process of dipping fittings into a nitric acid solution to rapidly form a chromium oxide on the surface of the material, creating a passive film that protects stainless from further oxidation (see PASSIVE FILM). The purpose of passivation is to remove both grease left from manufacturing and traces of steel particles which may have rubbed off manufacturing tools onto the fitting. In common commercial terms (meaning non-military and aerospace), passivating means cleaning to users, and the terms "passivating" and "cleaning" are used interchangeably. A wide range of cleaning methods using different mixtures containing nitric, phosphoric and other acids or simply exposing cleaned stainless fittings to air for a period of time will result in a "passivated" condition. For fittings that have been properly cleaned, it is impossible to determine the method of cleaning or passivation that was used. AN/MS/NAS fittings sold by SUNCOR have been cleaned, descaled, and passivated to the applicable engineering specifications.
Acid treatment of stainless steel to remove contaminants and improve corrosion resistance.