CORROSION RESISTANCE OF ELECTROPOLISHED SURFACES

Quite often in everyday service ‘stainless’ steels stain and ‘rustless’ alloys rust. In particular, the straight chrome/iron nickel‐free alloys have frequently exhibited early signs of severe tarnishing in service. Electrolytic polishing enhances the corrosion resistance of certain metals by forming very thin passive films—probably oxides—on these surfaces. This applies mainly to ferritic stainless alloys but also to some of the austenitic steels, to aluminium, brasses and to certain carbon steels. This article considers the nature and properties of the films and discusses practical applications.