REPAIRING OF OXIDE FILMS ON Zn-55 Al ALLOY COATED STEEL AFTER REMOVAL WITH PHOTON RUPTURE IN SOLUTIONS

摘要

A photon rupture, focused one pulse of pulsed YAG-laser irradiation, technique was attempt to investigate abrupt destroyed and repair of passive oxide films on Zn - 55 mass% Al coated steels. The specimens were irradiated with a focused one pulse of pulsed Nd -YAG laser beam at a constant potential in borate solutions, pH = 9.2, with and without Cl~-, NO_3~- and SO_4~(2-) ions monitoring current transients. The oxide films were reformed in the borate solution with NO_3 ~- and SO_4~(2-) ions after removal of the oxide film. As potential becomes nobler, current and peak current increase. These behavior can be explained by a preferential dissolution of the metal substrate, which is enhanced at nobler potential and anions. In Cl~- containing solutions, localized corrosion of coated layer occurs at high potential, while film reformation occurs at low potentials .