Abstract
The corrosion behaviour of coloured films on stainless steel formed by chemical, INCO and a.c. processes were investigated in HCI solution. Anodic polarization and a.c. impedance measurements were employed to characterize the pitting corrosion of various coloured films. Experimental results showed that the pitting resistance of coloured films increase in the order of chemical, a.c. and INCO process. The cathodic hardening treatment in either the INCO or the a.c. process acted to restrict the diffusion of reactive species in the coloured film and to improve markedly the corrosion resistance of coloured stainless steel. The a.c. impedance technique is demonstrated to be a very useful tool for the in-situ measurements of localized corrosion of coloured films and for the evaluation of the characteristic parameters in the corrosion system.