| 摘要 |
PROBLEM TO BE SOLVED: To perfectly remove a film by a practical means by partially removing an organic insulating layer in a substrate obtd. by forming an organic insulating layer on a metallic sheet coated with a rust preventive film composed of a chromium-contg. metallic layer and a chromium oxide layer, thereafter exposing the rust preventive film to a soln. or gas of halogen ions and then exposing the same to an alkaline soln. of permanganic acid. SOLUTION: As a soln. contg. halogen ions, hydrochloric acid is desirable since its rate for partially removing a chromium oxide layer is high. The concn. of chlorine ions is 3 to 36% as the aq. soln., and the temp. of the soln. is 15 to 50 deg.C. After the partial removal of the chromium oxide layer, the substrate is immersed into a heated alkaline soln of permanganic acid, by which the chromium metal or chromium alloy layer is efficiently removed, and a metallic sheet is exposed. As for the conditions of the alkaline soln. of permanganic acid, e.g., the concn. of potassium permanganate is 20 to 75g/l, the concn. of caustic soda is 20 to 50 g/l as the aq. soln., and the temp. is 20 to 90 deg.C.
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