Effect of pH and Chloride Ion Concentration on Inhibitor Storage in Amorphous Al-Co-Ce Alloys

Abstract The inhibitor storage in Al-Co-Ce alloys was investigated using surface analytical techniques including x-ray photoelectron spectroscopy, angle-resolved x-ray photoelectron spectroscopy, and Auger electron spectroscopy coupled with depth profiling. The composition of the native oxide was different from that of the bulk alloy indicating alloying element enrichment (Ce) and depletion (Co) in the oxide layer. Upon exposure to the environment, the oxide layer composition and thickness significantly changed depending on the pH and chloride ion concentration of the solution. For example, under highly acidic conditions, the Ce and Co content dramatically decreased. The pH-dependent solubility of the alloying elements, the thermodynamic driving force for oxide formation, and the oxide dissolution rate were found to be crucial factors in determining which alloying element was depleted or enriched in the oxide layer and in determining the changes in oxide thickness. The chloride concentration of the soluti...