| 摘要 |
PURPOSE:To form a surface layer wettable well with water, having superior corrosion resistance, and gathering no white rust on the surface of an Al material by applying an aqueous soln. of an alkali metallic silicate contg. a borate to the surface of the Al material, drying the soln., applying an aqueous soln. of an acidic compound, and drying the soln. CONSTITUTION:An aqueous soln. or dispersion of an alkali metallic silicate such as potassium silicate contg. a borate such as KBO2 is applied to the surface of an Al fin material for a heat exchanger and dried to form a film by 0.1-2.0g/m<2>. An aqueous soln. of one or more kinds of acidic compounds selected among inorg. acids, org. acids and acidic salts thereof such as an aqueous soln. of phosphoric acid is then applied and dried. The amount of the aqueous soln. applied is 10-50mg/m<2> (expressed in terms of the acidic compound), and the surface of the resulting film is made acidic. By this method, a corrosion resistant film wettable with water can be formed on the surface of the Al material. |
