中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 29 No. 6 June 2019 |
（1. Department of Mining and Materials Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand;
2. Center of Excellence in Materials Engineering (CEME), Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand;
3. Faculty of Science and Industrial Technology, Prince of Songkla University, Surat Thani Campus, Surat Thani 84000, Thailand）
Abstract:The anodizing parameters of voltage, current density, temperature, and electrolyte choice were assessed to find an appropriate combination for the superheated slurry cast 7075 Al alloy substrate. The alloy was anodized in sulfuric acid electrolyte or alternatively in sulfuric acid mixed with boric acid or citric acid. The voltages applied were in the range of 15-30 V. Anodizing current densities tested were 2 and 3 A/dm2, while temperatures tested were 5 and 15 °C. Thickness, surface morphology, hardness, and corrosion resistance of the oxide film were then evaluated. It was found that 25 V, 2 A/dm2 and 5 °C were suitable for this alloy when anodized in sulfuric acid. The oxide film was smooth with uniform thickness, low porosity, high hardness, and had the highest corrosion resistance at these parameters. However, discontinuous oxide films were observed from samples anodized at higher temperature of 15 °C. Alternative electrolytes considered were sulfuric acid mixed with boric acid or citric acid. The results showed that electrolytes with boric acid or citric acid increased thickness, hardness, corrosion resistance and quality of the oxide films. However, these oxide films were inferior to those obtained with sulfuric acid electrolyte at lower temperature (25 V, 2 A/dm2 and 5 °C).
Key words: 7075 aluminum alloy; superheated slurry casting; anodization; oxide film; anodizing parameters
