| 摘要 |
PURPOSE:To form a silicate film excellent in whitening resistance by means of a short-time treatment by treating an Al material with specific alkali silicate, baking the above under specific conditions, and then applying dealkalization to the above by using an aqueous solution of nitric acid. CONSTITUTION:Al and Al alloy are treated with alkali silicate in which the ratio of SiO2 to M2O (where M means alkali metals, such as Li, Na, and K) is regulated to >=1, preferably >= about 3. After the above treatment, baking is applied to the above without delay at 200-300 deg.C for 1min-5sec without drying the coated film. Subsequently, the resulting silicate film is subjected to dealkalization treatment by means of an about 10-30% aqueous solution of nitric acid and the film is stabilized. Then, water washing and drying are directly applied to the above, by which the silicate film excellent in whitening resistance can be obtained. |
