Abstract
A photon rupture method, film removal by a focused one pulse of pulsed Nd-YAG laser beam irradiation, has been applied to investigate initial stage of localized dissolution of Zn and Zn-Al alloy coated steels, which were formed nitrocellulose films as a protective film, in 0. 5kmol m-3 H3BO3-0. 05kmol m-3 Na2B4O7 (pH=7. 4) with 0. 01kmol m-3 chloride ions. This method can remove oxide films and nitrocellulose films on coated layer by laser ablation without any contamination from film removing tools, and the removing speed is extremely high. At low applied potentials, all samples reformed oxide film after films were removed by this method. The oxide film formation kinetics follows on inverse logarithmic law in agreement with Cabrera-Mott theory. However, as increasing applied potential, after some period, localized dissolution occur at nitrocellulose films were removed area. The peak currents of Zn-5mass%Al coated steel specimens were larger than those of Zn and Zn-5mass%Al coated specimens. This result suggest that high aluminum containing coated layer does not show good corro-sion resistance in frequently oxide film removal environments.
