Study On Pulse Hard Anodizing Processing For Aluminum And Aluminum Alloy

Hard anodizing is one of the hotspot of anodizing. The temperature of hard anodizing process of aluminum alloy applied to industry is generally very low. It wastes energy because of using refrigeration equipment, thus it will increase production costs. Therefore, it is a focus on how to carry out pulse hard anodizing for aluminum alloy at room temperature.In this paper, pulse hard anodizing process for 2A12 aluminum alloy was investigated at room temperature. The mechanical property, structure feature, morphology analysis and phase component of the hard anodic oxidation film were investigated by micro-hardness tester, metalloscope, SEM and EDS. Sulfate was the main component of the electrolyte. A better electrolyte formula was optimized by orthogonal test with the addition of Oxalic acid, Tartaric acid, Triethanolamine and Aluminum Sulphate. The optimized electrolyte formula in this study was as followed: Sulfate 280g/L, Oxalic acid 30g/L, Tartaric acid 50g/L, Triethanolamine 50g/L, Aluminum Sulphate 7g/L. The pulse hard anodic oxidation film was obtained at room temperature by using the optimized electrolyte formula. The hardness and thickness of the hard anodic oxidation film were HV528 and 34μm respectively. It had a better corrosion resistance. Various processing parameters (including current density, oxidation time and duty cycle) which affected the morphology performance of pulse hard anodic oxide film of 2A12 aluminum alloy were investigated by orthogonal test at room temperature in the basis of optimized electrolyte formula. The optimized processing parameters were as followed: oxidation time 50min, current density 3A/ dm2, duty cycle 75%. The hardness and thickness of hard anodic oxidation film obtained by pulse hard anodizing were 540HV and 66μm respectively, furthermore, it had excellent comprehensive performances. The mechanism of adding hard particles to the electrolyte was investigated preliminary.In addition, the processing parameters which affected the performance of pulse hard anodic oxide coatings on industrial aluminum were investigated by orthogonal test at room temperature. Copper could be loaded in oxidation coating by using anodizing-plating method in the electrolyte which contained Sulfuric acid and copper sulfate. It was able to increase the hardness of the film.