| Because aluminum has many excellent properties of physical andchemical, it is widely applied to various fields of national economy. However,the natural oxide film formed on the surface was susceptible to corrosion,which will greatly reduce its service life. Thus anodizing technology wasused to improve various properties such as corrosion resistance andmechanical properties of the aluminum surface in industrial sector. Thisarticle researches the following three aspects:1. Optimize Sulfuric-tartaric acid anodizing processOptimize the process parameters of anodization by studying impact ofthe time, temperature, voltage on the oxide film SEM, thickness, hardness,corrosion resistant. The anodization films appear an amorphous phase,containing the-A2O3﹑α-A2O3by X-ray diffraction (XRD) analysis. Withoxidation voltage increases, the pore size increases, when the voltageincreased to18V, the size of pore is35nm; the hardness first increases thendecreases, maximum reached to160HV when the voltage was16V. Withincreasing oxidation time, the thickness of the anodized aluminum filmincreases almost linearly; surface hardness increased with time showed adecreasing trend after the first increase in the oxidation time of30min, theoxide film hardness of118HV; oxidation time was30min, the anodic oxidefilm is formed on the passivation film etching process, the etching rate of5.0×10-7A/cm2．With the increase of oxidation temperature, the first increaseoxide film thickness decreases, when the temperature is47℃anodicoxidation, the thickness of up to17um; when the temperature is37℃，thehardness of anodization films is118HV and its corrosion potentialreach-0.74V.The optimum conditions sulfuric-tartaric acid anodization is16V,37℃,30min.2. Optimize Sulfuric-citric acid anodizing processTime, temperature and voltage on the oxide film surface morphology, thickness, hardness and resistance to corrosion were systematic studied.Studies show that, with the increase of the anodizing voltage, the anodi zationfilm gradually becomes yellowish white, and the aperture increases. Themaximum size of pore was25nm when voltage achieved to18V. With theincrease of the oxidation time, the thickness of the anodized film increasesalmost linearly. When the oxidation time increased to60min, the thickness ofanodization film was19.8μm; when the oxidation time is40min, corrosionresistance was preferably and the film resistance is1.87×105Ωcm2. With theincrease of the temperature, the oxide film thickness increases, which was17.5μmwhen the oxidation temperature was up to47℃. corrosion resistance was preferablyas the oxidation temperature is37℃, which corrosion potential was-0.73V,necessarily go with the corrosion rate was2.51×10-6A/cm2.3. Study on seal condition of anodization filmStudy effects of different seal process on the anodization film. Anti-corrosion ofanodization film: sealed anodization film> anodization film> aluminum.Anti-corrosion of anodization film with sulfuric-tartaric acid: cerium sealed>nickel salts sealed> Hot sealed> not sealed. For cerium salt sealed anodizationfilm which own the better anti-corrosion3resistance, with the immersion time in3.5%NaCl solution, the corrosion rate increased1.58×10-9A/cm2to1.0×10-7A/cm2, so corrosion becomes getting worse.Anti-corrosion of anodization film with sulfuric-citric acid: cerium sealed>nickel salts sealed> Hot sealed> not sealed. For cerium salt anodization film,corrosion rate increases3.16×10-8A/cm2to3.1×10-6A/cm2, which the worsethe corrosion resistance. |
PDF Full Text Request