PHOTOELECTROCHEMICAL APPROACH TO PASSIVITY.

Abstract

Most passive metals show photoeffects due to excitation processes within the electrode which cause a change in electrochemical behaviour. In most cases light induces electron-hole pair formation in the passive layer which is semiconducting or insulating. Excitation in the underlying metal followed by photoemission is observed as well. The parameters which influence wavelength and potential dependence of the photocurrent are discussed. Typical examples of passive metals which belong to transition metals, noble metals and valve metals are described. From the discussion it can be inferred that photoelectrochemistry could develop to a powerful in-situ method to characterize passive films. (Author abstract. )