Pickling

Pickling metal is a process intended to dissolve heavy oxides and contaminates, and remove the effects that real-world handling has on the surface of stainless steel. The real-world fabrication, welding and handling of stainless steel components will leave surface contaminates. These contaminates, which may include weld oxides, scale and embedded particles, will hinder stainless steel’s natural ability to resist corrosion.

Pickling vs. Passivation

Both pickling and passivation are intended to remove surface contaminates and improve the corrosion resistance of stainless steel. Pickling utilizes aggressive acids (usually a mixture of nitric and hydrofluoric acid) to dissolve heavy scale, weld oxides and other surface contaminates. Passivation solutions (citric or nitric acid) are not as aggressive and are not intended nor are capable of dissolving heavy scale and surface oxides. Passivation is generally a cleaner and more controlled process, with parameters defined by ASTM standards. Thus pickling is used prior to or in lieu of passivation when the material has heavy contaminates or oxides.