| 摘要 |
PROBLEM TO BE SOLVED: To improve the adhesion of a coated film at the time of coating of an Al product and the corrosion resistance after coating by forming a synthetic film, composed of nonporous anodic oxide film and boehmite film, on the surface of an Al product. SOLUTION: The surface of a stock, such as sheet and casting, or press formed part, etc., of pure Al or Al-type metal such as Al-Mn alloy is degreased with an alkalescent degreasing solution and successively pickled to undergo cleaning. Subsequently, boehmite treatment is performed to form a boehmite film of 700-3000Åthickness, and further, an electric current is applied by using the Al material as anode in an electrolyte in which boric acid, adipate, phthalate, etc., are dissolved to form a nonporous anodic oxide film of 70-2000Åthickness as an undercoat layer for boehmite film. At the time of coating the Al material, this synthetic film is previously baked to undergo heating and drying, by which moisture content is regulated to <=5wt.%. A thermoplastic acrylic resin type coating material is applied to the surface of this Al material.
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