EFFECT OF ELECTRICAL TRANSIENT COUPLING PHENOMENA ON THE INITIATION OF PITS BY A PULSED LASER

This paper will be devoted to an analysis of the consequences of electrical coupling phenomena on the electrochemical parameters observed during transient events of pitting corrosion, i.e., during the initiation and the repassivation. The effects of the coupling phenomena on the stability of the pit were also studied in free corrosion potential. From an experimental point of view, pitting events were initiated with a pulsed laser beam. A formal description of the effect of the coupling phenomena between the pit and its vicinity on the electrochemical measurements is given. Current and potential variations related to the pitting event must be carefully interpreted because the actual pit current could be distorted before reaching the measurement setting. Regarding the stability of the pit, because the capacitance of the surrounding area of the corroded site interacts with the transient corrosion reaction, the free potential drop is less important if the passive area is greater, increasing the likelihood of propagation of the pit embryo.