Surface-treated aluminum material and method for its surface treatment

摘要

An aluminum material is surface-treated with an aqueous solution containing 0.005 mol/lit. or more of a chelating agent and 5 g/lit. or more of an organic amine and having 100 ppm or less of phosphoric acid radical ion concentration and 500 ppm or less of sulfuric acid radical ion concentration, until its surface has a color tone (S) of: S=(X2+(3.388Z-3Y2)1/2>/=70 wherein X, Y and Z represent the tristimulus values of color. The aluminum material can be surface-treated while setting the treating conditions on the basis of a specific color tone detectable by colorimetry, without relying on experience and intuition. The surface-treated aluminum material can have a good anticorrosion, have good color change preventive properties, a good adhesion of coatings and a beautiful surface appearance. The present surface treatment is effective as anticorrosive treatment for itself, but can be also effective when this treatment is carried out as a pretreatment and further surface treatment is carried out thereon.