Evolution of Microstructure of Hard Anodized Film on Aluminium Alloy 6061 in Low Sulfuric Acid Electrolyte

Hard anodic oxide film grew on aluminum alloy 6061 in unconventional sulfuric acid concentration electrolyte containing 1%, 2%, 3%, 4% and 5%H₂SO₄ (Wt.%) with special apparatus.The results indicate that the surface roughness values and microhardness values of the anodic oxide film obviously decrease with the increase in acid concentration, and the size of pores in the anodic oxide film becomes large.Compared with the anodic oxide film at sulfuric acid concentration electrolyte containing 1% H₂SO₄ and 2% H₂SO₄, the anodic oxide film obtained in 3% H₂SO₄ sulfuric acid concentration electrolyte has fairly better-distributed homogeneous degree.However 3% H₂SO₄ sulfuric acid concentration electrolyte is suitable for the hard anodic oxidation process of aluminum alloy 6061.