Corrosion behaviour of Al Ti coating elaborated by cathodic are PVD process onto mild steel substrate

The use of cadmium coatings in industry is strongly restricted by an Europe an directive, cadmium being dangerous for human health and the environment. Aluminium-based coatings are potential candidates for replacing cadmium co atings. In this paper. we compare the corrosion behaviour of Al and Al/Ti c oated steel. We demonstrate that the galvanic effect through the open poros ity of the Al coating leads to a rapid loss of sacrificial protection durin g long immersion time. It is shown that the double-layer coating Al/Ti/stee l presents a better corrosion resistance than monolayer in coating in salin e solution. The intermediate titanium layer permits the reduction of the op en porosity and also allows the reduction of the galvanic effect between st eel and aluminium. In order to enhance the electrochemical properties of th e: double-layer coating we also investigated the effect of PVD post-oxidati on treatments. (C) 1999 Elsevier Science S.A. All rights reserved.