Abstract
Measurement of PZC of aluminium in chloride water by surface tension meniscus method produced two situations of PZC, one in the cathodic region and other in the anodic region, when the metal was polarized cathodically or anodically. PZC was dependent on the chloride content of the solution in the cathodic and anodic sides. To confirm these facts, PZC was determined by potential build-up and decay methods, based on double-layer capacitance minima at the solid/liquid interface. Both methods confirmed the occurrence of two situations of zero charge in aluminum chloride water system. As a function of chloride content, PZC reveals that specific adsorption of chloride ions is involved during passivity and passivity breakdown with the formation of two types of pitting, anodic and cathodic pitting. The phenomena of local pH change at the solid/liquid interface along with the conductivity maxima/minima of the bulk solution during the cathodic/anodic passivity breakdown, as obtained from earlier works, helped in understanding the occurrence of PZC and passivity breakdown.
