Study On Hard Anodizing And Growth Regularity Of Oxidation Film On Aluminum Alloy

2024aluminum alloy is the most widely used as a high strength aviation aluminum alloy in Al-Cu-Mg hard aluminum, what is more,2024aluminum alloy is used in hard anodic oxidation commonly. Because it contains high content of copper, which happened to burning and pulverization easily in oxidize process. At present, the maturer hard anodic oxidation process applied to industrial production under low temperature, which needed refrigeration equipment to control temperature, caused great waste of energy resource and increased costs of the production.so it was the favor for enterprise to obtain high quality hard oxidation films at room temperature.In this paper, hard anodizing process for2024aluminum alloy was investigated at room temperature. Analysis and characterization of the oxidation films used the micro-hardness testing, SEM and EDS and XRD. Sulfuric acid was the basic electrolyte and joined the organic acid modification, the effects of electrolyte components to performance of oxidation films though orthogonal experiment and single factor experiment research, the electrolyte formula was as followed:sulfuric acid10%(volume fraction), oxalic acid30g/L, tartaric acid30～40g/L. The hard anodic oxidation film was obtained at room temperature by using the dc superposition pulse anodic oxidation at constant current density. The hardness and thickness of the hard anodic oxidation film were HV350and50μm.The oxidation processing was optimized in the optimized the electrolyte. The optimized processing parameters were as followed:current density2A/dm2, oxidation time50min, pulse frequency25Hz, pulse duty cycle70%and pulse amplitude25%. The hardness and thickness of the hard anodic oxidation film were HV360and55μm.The effects of electrical parameter (current density, pulse duty cycle, pulse amplitude and pulse frequency) and electrolyte system were studied to the growth regularity of oxidation films. The results indicated that the oxidation film thickness grew inside the base material was always more than outside, whether in a single sulfuric acid system, three acid system, or three acid system with conductive salt. The percentage of the oxidation film thickness grew to the base material was51%～65%. The electrical parameter had no obvious effects on the growth regularity of oxidation films, which could provide reference for the actual parts processing tolerance size design.In addition, three post-processing way was researched to the effects of oxidation films, which was boiling water sealing, heating inlaying and heating baking. It was found that the hardness of oxidation films decreased by boiling water sealing, increased by heating inlaying and heating baking.