Studies On Technology And Properities Of Hard Anodizing Of2A12Aluminum

For2A12high-alloy aluminum, the hard anodizing technology is studied in sulphuricacid solution. The microstructure, film thickness, film surface roughness, hardnessand abrasive property is observed and analyzed by optical microscopy, SEM,microhardness tester, roughness instrument and Taber abrasive tester etc.Difference of film thickness is studied, the results show that the coarse crystal andfine crystal area of aluminum alloy material lead vary film growth rate. So filmthickness is differ on various area of aluminum alloy.Stringent requirement of hardness and surface roughness of2A12aluminum alloyhard anodizing film is performed during foreign trade manufacture, and the chromateacid anodizing coating as maskant is requirement before hard anodizing. For thesespecific requirement, the technique of hard anodizing of improving the film thicknessuniformity, hardness and surface roughness were studied.2A12Al alloy anodizingprocess in pure sulphuric acid solution were optimized by DOE （Design ofExperiment）. The optimal process scheme in sulphuric acid solution is as follows:sulphuric acid concentration of330g/L, current density of2.5A/dm2, anodizingtemperature of-3℃, ramp time of20min, anodizing time of60min.The surface roughness correlate the large cavities. Study result show that dissolution ofalloy may be reduced in initial stage by control ramp time during hard anodizingprocess. So lower cavities rate film generate. The surface roughness then conform tothe requirement.