The thin metal layer of the steel surface is removed. A mixture of nitric hydrofluoric acid is typically used for the production of the stainless steels. The drilling is performed to remove the starting color from the defective blocks in which area the chromium content of the surface of the steel is reduced.
Also, mind creation of the ovaries, e. g. after heat treatment, are removed with a vapor.
Surface area of stainless steels in generally passive by itself. Under certain conditions, however, it may be desirable to promote this process by acidifying acid. In contrast to vaporization, there is no material in passivation. However, the quality and thickness of the passivation layer is targeted optimally.
Under certain conditions there is no passivation and pickling at the same time but separated by acid treatment processes. In this proces, the nitric acid used produces only a slight milling effect on the stainless steel and serves essentially to passivation.