XPS and EPMA studies on self-healing mechanism of a protective film composed of hydrated cerium(III) oxide and sodium phosphate on zinc

Abstract A thin, protective film was prepared on a zinc electrode by coverage with a hydrated Ce2O3 layer and 0.0552 mg/cm2 of a Na3PO4 · 12H2O deposit layer and by drying the layers at 90 °C for 23 h, as has been reported in the preceding paper. This film was highly self-healing at the scratched electrode in an aerated 0.5 M NaCl solution for many hours. The present investigation deals with elucidation on self-healing mechanism of this film by X-ray photoelectron spectroscopy and electron-probe microanalysis. The scratched surface was covered with deposits of Zn(OH)2, ZnO and small amount of Zn3(PO4)2. Both cathodic and anodic processes of zinc corrosion were markedly suppressed by coverage of the scratches with the deposits, resulting in the self-healing activity at the scratched electrode in 0.5 M NaCl.