Stainless steel is relatively free of the iron hydrates
Stainless steel (SS) is relatively free of the iron hydrates that are a common component on the surface of regular grades of carbon steel.SS should be cleaned to remove the surface oils and dirt from manufacturing and handling. Many stainless steel products do not have a protective coating because they are not sensitive to ordinary atmospheric conditions.
The passive oxide layer on stainless steel is relatively inert to alkaline cleaners and other chemical products that are commonly used on carbon steel. Normal cleaning will remove lose soils but it will not create a surface that is receptive to iron phosphating.
Acid etchants or mechanical abrasion processes are sometimes used to remove the oxide layer and create a slightly roughed surface that is better for adhesion of the coating. These processes help promote adhesion but they do not provide any additional resistance to moisture penetration.