| 摘要 |
PURPOSE:To stabilize the pH of a chemical conversion liquid over a long period of time and to obtain chemical conversion foil having stabilized quality by forming aluminum foil for an electrolytic capacitor by chemical conversion using the chemical conversion liquid which is adjusted in pH by adding urea thereto. CONSTITUTION:The pH of the chemical conversion liquid is adjusted by adding urea to said liquid as an alkaline source for the chemical conversion liquid in the stage of forming the aluminum foil for the electrolytic capacitor by the chemical conversion using the chemical conversion liquid. The urea accelerates hydrolysis to generate quickly NH3 when the pH decreases from 7. The decomposition rate is decreased when the pH exceeds 7, thus the urea stabilizes the pH of the chemical conversion liquid in an about 6.5-7.5 range. The above-mentioned method is applicable for the chemical conversion liquid of a phosphoric acid, boric acid, carboxylic acid, etc. |
