Study On Technology Of High Silicon Aluminum Alloy Anodizing By Phosphomolybdic Acid

Interaction between oxygen and surface of aluminum and aluminum alloy could form an oxidation film (0.01 μm～0.05μm) in atmosphere. Though the natural oxidation film could keep from corrosion of atmosphere, it is a film that is amorphous, uneven, discontinuous, it is not credible protective and decorative film. We usually take anodizing measures to form Al2O3 deactivation film. Anodic oxidation film is much more thick than natural oxidation film, and it is porous structure. So it conductive superficial rendering and enhance coating cohesion for improving surface hardness, abrasion resistance. Obtaining of oxidation film have many methods. At present, sulfuric acid anodic oxidation is extensively applied at home and abroad. It have obvious superiority in production costs, oxidation film characteristic and performance compared with anodic oxidation of other acids.This paper research anodic oxidation of the high silicon aluminum alloy of silicon content between 13 percent and 15 percent in phosphomolybdic acid hydrate electrolyte. Study on the effect of anodic film from anodic oxidation technology factors by designing orthogonal experiment. Determining optimal anodic oxidation crafts condition by uniform, color, alkali resistance as indicators. The optimal crafts condition:electrolyte concentration is 250g/L, additive concentration is 8g/L, oxidation times is 30min, oxidation temperature is 25℃, anodizing voltage is 110V.Conducting analysis and comparison for microcosmic morphology, ingredient of oxide film by SEM, EDS, XRD. The results show that the oxidation film is uniform and dense. It have resistance to alkali. Oxide film is mainly composed of alumina. Its thick is about 2μm. It do not fade when oxidation film is rubbed in metallographic abrasive paper. The result show that abrasion performance is good. Study on electrochemistry behavior of oxidation film in Bode and polarization curve. The results show that the enhancing of corrosion resistance after oxidation film sealing in optimal condition.