March 3, 2011

Chromic Acid Anodizing

Chromic acid anodizing is coating process on the metal that refer to both method of chromium electroplating and anodizing process, this process if frequency referred to as type I anodizing as designated by the MIL-A-8625 standard. It is also covered in the AMS 2470 and the ASTM B580 specifications. By chromic acid anodizing enhances the corrosion resistance of aluminum parts and produces a thin opaque film that is soft, ductile, non-conductive, and to a degree self healing. The result thickness after using this process usually about 0.00005 to 0.0001 inches or 0.00125 mm to 0.0025 mm.

Chromic acid anodizing may be applied as a pre-treatment before painting to enhance adhesion and it is harder to dye that sulfuric acid anodize. After the metal being chromic acid anodize has over other anodizing process is that it does not lower the fatigue strength of the aluminum or damage the base material if it is entrapped in lap joints or blind holes. As other anodizing process, after chromic acid anodize the solution may be sealed in either hot water or sodium dichromate solutions.

Ther are three type of chromic acid anodizing, type I is this layer of anodized film or oxide film, while type II and type III will result of hard anodized film on the surface.

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