A self-healing protective film prepared on zinc by treatment in a Ce(NO3)3 solution and modification with Ce(NO3)3

A self-healing protective film was prepared on a zinc electrode by treatment in 1 × 10−3 M Ce(NO3)3 at 30 °C for 30 min to form a thin layer of hydrated Ce2O3 and by modification with 114 μg/cm2 of Ce(NO3)3 · 6H2O. The film was dried at 30 °C under a dry atmosphere. After the electrode surface was scratched with a knife-edge crosswise and immersed in an aerated 0.5 M NaCl solution at 30 °C for many hours, polarization measurement of the electrode was carried out in the NaCl solution. The protective efficiency of the film was markedly high, 97.7% at the immersion time, ti=24 h. Neither pit-like anodic dissolution feature nor pit was observed within the scratches at ti=72 h. X-ray photoelectron spectroscopy and electron-probe microanalysis revealed that Ce3+ migrating into the scratches from the film was adsorbed on the hydrated or hydroxylated zinc surface to form a new layer of hydrated Ce2O3 within the scratches, resulting in the self-healing activity of the film for preventing zinc corrosion at the scratched surface.