CHARACTERIZATION OF PASSIVE FILMS ON ZINC ELECTRODES BY IMPEDANCE MEASUREMENTS AND XPS

H. MISHIMA,; B. A. LÓPEZ DE MISHIMA,; E. SANTOS; C. P. DE PAULI,; K. AZUMI; N. SATO

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1991 vol. 36 p. 1499 - 1991

0013-4686

Abstract—The behaviour of the passivating layers formed by anodic polarization on zinc electrodes inborate and arsenate and in borate arsenate mixture solutions of pH 8.9 was studied by means of impedance measurements and XPS analysis. An equivalent circuit for the system is employed for the data fitting. Since an analysis based on the Mott-Schottky relationship leads to an excessively high carrier density with respect to the corresponding resistivity valué, the potential drop should occur through the whole passive film. In accordance with the XPS results, a model can be proposed consisting of a layer of hydrated zinc oxide which should be responsible for the passivation. The passivating film on zinc electrodes has a more protective effect when it is formed in borate 0.1 M and arsenate 0.1 M solutions than in arsenate 0.5 M solutions.