Self-healing protective films prepared on zinc electrodes by treatment in a cerium(III) nitrate solution and modification with sodium phosphate and calcium or magnesium nitrate

Self-healing protective films were prepared on a zinc electrode by treatment in a Ce(NO3)3 solution and modification with Na3PO4 and Ca(NO3)2 or Mg(NO3)2. The protective and self-healing abilities of the films were examined by polarization measurements and observation of pit formation after the electrode was scratched with a knife-edge and immersed in aerated 0.5 M NaCl for many hours. The protective efficiency of the film modified with Ca(NO3)2 was higher than that of the film without Ca(NO3)2 but the self-healing ability of the former film was not sufficiently high during the prolonged immersion. Mechanisms of the protective and self-healing activities were discussed using X-ray photoelectron spectroscopy and electron-probe microanalysis.