Corrosion of CrN and TiAlN coatings in chloride-containing atmospheres

Chromium and titanium-aluminium nitrides were deposited, by physical vapour deposition techniques, on stainless steel substrates and their corrosion b ehaviour was studied in two different environments: a gaseous environment c ontaining HCl at a temperature of 350 degrees C and a 1 M HCl aqueous solut ion environment, at room temperature. X-ray photoelectron spectroscopy was used to study the mechanism of the reactions that occurred in the gaseous e nvironment. This analysis shows an oxidation of the surface caused by the s ubstitution of nitrogen by oxygen. Open circuit potential and potentiodynam ic polarisation measurements were performed in the aqueous solution environ ment. The aqueous corrosion behaviour of the nitride coatings is strongly d ependent on the microdefect density of the coating. (C) 1999 Elsevier Scien ce S.A. All rights reserved.