7075 aluminum alloy hard anodizing

Jun 12, 2023

Hard anodization is a thick film anodization process, which is a special anodizing surface treatment process for aluminum and aluminum alloys. In this process, the maximum thickness of the anodized film can be up to about 250 microns, and a microhardness oxide film of 1500 kg/mm2 can be obtained on pure aluminum, and 400 to 600 kg/mm2 can be obtained on the aluminum alloy. Microhardness oxide film. The hardness value, the inner layer of the oxide film is larger than the outer layer, that is, the barrier layer is larger than the oxide film layer with pores, and there are loose pores in the oxide film, which can adsorb various lubricants, increase the friction reducing ability, and the thermal conductivity of the oxide film layer is very high. Poor, its melting point is 2050 ° C, the coefficient of resistance is large, the sealing treatment (immersion insulation or paraffin) breakdown voltage can reach 2000V, high corrosion resistance in the atmosphere, high wear resistance, is also a The ideal thermal insulation film layer also has good insulation properties and has a series of advantages such as strong bonding with the base metal. Therefore, it has been widely used in the defense industry and mechanical parts manufacturing industry.



The hard oxidation process is used to replace the traditional hard chrome plating. Compared with the hard chrome process and the cyanide-free galvanizing process, it has the advantages of low cost, firm film bonding, convenient plating solution and convenient treatment of cleaning waste liquid.
7075 aluminum alloy is a cold-treated forging alloy with high strength, far better than mild steel. 7075 is one of the more powerful alloys for commercial use. 7075 aluminum alloy has a compact structure, strong corrosion resistance, good mechanical properties and anode reaction. The fine grain makes the deep drilling performance better, the tool wear resistance is enhanced, and the thread rolling is more distinctive.
However, the surface hardness of the 7075 aluminum alloy is low and it is not wear-resistant. The application range is limited. The hard anodizing (anodic hardening) treatment of the 7075 aluminum alloy can obtain a film layer with good adhesion to the substrate and a certain thickness. Used in aluminum transmission splines, bearing mounting positions, threaded fastenings, etc.
After anodic hardening of 7075 aluminum alloy, the thickness of the oxide film can be 30μm-50μm, and the hardness is 50-55HRC, which can make the aluminum material meet the spline requirements. (The electrolyte is oxalic acid, DC, the electrolysis temperature is below 0 °C, and the oxidized color is yellowish green with metallic luster)。