ANODIC DEFECT FORMATION, NONSTOICHIOMETRY, AND PHASE-TRANSFORMATIONS IN OXIDE-FILMS ON NICKEL IN ACID-SOLUTION

Anodic defect formation in oxide films on nickel in acid solution is studied using photoelectric recombination technique in conjunction with resistometry and potentiometry. Anodic nickel dissolution in acid solution is shown to proceed with the participation of a surface oxide whose nonstoichiometry and defect structure vary with the potential. Anodic boundaries of the stability region for oxide phases on nickel are determined with respect to both an oxygen and a metal excess. Potentials of the oxide stability boundaries are demonstrated to correspond with the passivation potentials for nickel. Nonstoichiometry vs. potential diagrams are obtained, which allow the nature of prevailing nonstoichiometric defects and their concentration at different electrode potentials to be evaluated.