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Salt Spray Corrosion Properties of an Anodic Oxidation Film Produced on 7475 Aluminium Alloy by Laser Heat Treatment
D-H. Zhang, J-C. Wang and D-J. Kong

An anodic oxidation film on 7475 aluminium alloy was processed using a laser heat treatment. Thereafter the salt spray corrosion behaviours of the obtained anodic oxidation film were investigated with 5 ±0.5% NaCl solution. The surface–interface morphologies, compositions of chemical elements and phases of the anodic oxidation films were analysed. The chemical elements of the anodic oxidation film surface–interface after salt spray corrosion were examined and the effect of laser heat treatment on the anodic oxidation film structures and salt spray corrosion resistance were researched. The results show that the anodic oxidation film by laser heat treatment is primarily composed of Al2O3 and SiO2, while after salt spray corrosion the oxide layer is composed of Al2O3, the heat affected zone (HAZ) is primarily composed of Al2O3 before and after salt spray corrosion. The bonding form of compound plus diffusion is formed at the interface after salt spray corrosion, there are only a few pits, without spalling on the anodic oxidation film after laser heat treatment, showing high salt spray corrosion resistance.

Keywords: CO2 laser, 7475 aluminium alloy, anodic oxidation film, microstructure, phase, laser heat treatment, salt spray corrosion

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