THE INFLUENCE OF UV-LIGHT ON THE DISSOLUTION AND PASSIVE BEHAVIOR OF COPPER-CONTAINING ALLOYS IN CHLORIDE SOLUTIONS

The influence of UV light (300-450 nm) on the passive and dissolution behavior of copper alloys CA-715 and CDA-614 in dilute chloride-contai ning solutions was studied. A slight ennoblement in the breakdown pote ntial, an increase in the induction time, and considerably reduced ano dic current densities at potentials higher that the initial breakdown potential were observed for the illuminated electrode. These effects w ere observed regardless of whether the electrodes were illuminated con tinuously or illuminated only before the polarization scans. and appea r to be independent of the wavelength of the incident light in the wav elength region 300 to 450 nm. These findings are explained in terms of a photo-induced modification of the passive film formed on the copper -containing alloys in the dilute chloride solution, which render it mo re resistant to the onset of attack. This modification is explained in terms of the semiconducting nature of the passive film and the point defect model for the breakdown of passivity. (C) 1998 Elsevier Science Ltd. All rights reserved.