| 摘要 |
PROBLEM TO BE SOLVED: To chemically polish the surface of an Al-base metal without using phosphoric acid, nitric acid and their salts and without causing environmental pollution by using an aq. soln. highly alkalified with an alkali hydroxide and contg. a coating forming agent as an additive. SOLUTION: One or more additives are added to a highly alkaline aq. soln. of an alkali hydroxide, preferably sodium hydroxide or potassium hydroxide having about 0.2-2.0 mol/l concn. to prepare the objective chemical polishing soln. An Al-base metal freed of sticking fats and oils with a dilute alkaline aq. soln. is immersed in the chemical polishing soln. to polish the surface of the metal. The additives include a coating forming agent which forms a solid coating on the surface of the metal. A solid coating 4 is thinly formed on the fine protrusions 1 of the surface of the metal and thickly formed on the fine recesses 2, the fine protrusions 1 are selectively etched with a viscous thick coating 3 near the surface and the surface is made flat. The coating forming agent is preferably an oxidizing agent, silicates or borates.
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