Film formation on stainless steel in acidified dichromate solutions

Abstract

A process for producing decorative coatings on stainless steel, by immersion in a solution of chromic and sulphuric acids, has been studied. The composition of the film produced has been investigated using a number of spectroscopic techniques. Both alternating and direct current methods have been used to investigate the conduction properties of the film. The formation of the film in the dichromate solution results from a combination of the anodic process of steel oxidation and the cathodic process of dichromate reduction. The rates of these processes have been found to increase with time during the formation of the film, as does the rate öf film formation. A qualitative mechanism, which explains most of the experimental results, is proposed.