A thin protective layer was prepared on a zinc electrode by treatment in 1 × 10 −3 M Ce(NO 3) 3 at 30 °C for 30 min and modification in 1 × 10 −2 M H 2O 2 at 30 °C for 10 min. This layer was highly protective against corrosion of zinc in an aerated 0.5 M NaCl solution after immersion in the solution for many hours. The protective efficiencies of the modified layer were remarkably high, more than 96% in the region of the immersion time between 72 and 168 h and 94% at 720 h. The layer was composed of hydrated Ce 3+ oxide containing Ce 4+ which improved the protective ability of the layer.