Improvement in the self-healing ability of a protective film consisting of hydrated cerium(III) oxide and sodium phosphate layers on zinc

Abstract A self-healing protective film prepared on a zinc electrode by previous treatment in a Ce(NO 3 ) 3 solution and coverage with a Na 3 PO 4 layer was improved by the addition of Zn(NO 3 ) 2 . The protective and self-healing abilities of the films against corrosion of zinc in an aerated 0.5 M NaCl solution were examined by polarization measurements and observation of pit-like anodic dissolution feature (plf) and pit formation after the electrode was scratched with a knife-edge crosswise and immersed in the solution for many hours. The film prepared on the pretreated electrode coated with 9.98 or 19.9 μg/cm 2 of Zn(NO 3 ) 2 · 6H 2 O and 55.2 μg/cm 2 of Na 3 PO 4 · 12H 2 O was significantly protective and self-healing against zinc corrosion on the scratched electrode. The protective efficiency of the film was more than 96% in the region of the immersion time between 72 and 360 h. No plf was observed at the scratches after immersion for 120 h. Results of Fourier transform infrared reflection and X-ray photoelectron spectroscopies revealed that the film was composed of Na 3 PO 4 , Zn 3 (PO 4 ) 2 and Ce 2 O 3 layers.