On ships where the cargo tanks are made of stainless steel (such as chemical tankers), sometimes due to surface contamination of the steel surface the stainless steel may get exposed to corrosion. Passivation is the process for cleaning / treating the stainless steel cargo tanks with certain chemicals in order to ensure the anti-corrosion properties of the tanks is restored by formation of a thin anti-corrosive layer on the stainless steel surface.

A way to carry out passivation is by acid pickling and washing. Pickling is normally carried out by applying thin layer of picking paste which consists of nitric acid or nitric/ hydrofluoric acid mixtures. Thin layer is normally applied to spots in tank where surface contamination is evident.

Another way of carrying out pickling is to wash the tanks with solution of mixture of nitric acid and hydrofluoric acid. After 30 minutes, the tanks are washed using fresh water.