塩化物水溶液中におけるアルミニウムの界面インピーダンス

抄録

The impedance of the system aluminium-surface film-aqueous halide solution has been investigated by means of the apparatus consisting of a potentiostat and an A.C. bridge. The results obtained may be summarized as follows:
(1) The series capacitance component of the impedance between aluminium and the solutions of pH 9.26∼11.15 has a maximum value at the potential intermediate between the corrosion potential and the pitting potential of the specimens, namely approximate −1.15 V (vs.S.C.E.). Its series resistance component also has a minimum value at the same potential. These phenomena are considered to result from the decrease in thickness of the surface films near that potential. In neutral solutions, these phenomena are not observed.
(2) The dissipation factor (tanδ) of the surface film on aluminium formed anodically in aqueous halide solutions grows larger with increasing potential to the noble direction. It is suggested that the defect density in the surface film increases near the pitting potential of the specimen.
(3) A remarkable decrease in the impedance between the aluminium electrode and the solution is observed in the potential region of pitting dissolution. Since the impedance of the surface film itself dose not show a remarkable change, the above decrease in impedence is dominated by the Faradaic impedance induced by the pitting dissolution current.