| 摘要 |
PURPOSE:To improve the power to dissolve away hard and dense oxide scale by using a soln. mixture formed by adding thioglycol to a hydrochloric acid and sulfuric acid and adding further an L-ascorbic acid, etc. and an inhibitor for acid corrosion thereto. CONSTITUTION:A thioglycolic acid is added at about 0.2-2% to a hydrochloric acid or sulfuric acid alone or a soln. mixture thereof about 3-7% concn. A reducing agent composed of >=1 kind of an L-ascorbic acid and erythorbic acid is added at about 0.1-0.3% to said soln. with respect to a 0.5-2% concn. range of the thioglycolic acid and an inhibitor for acid corrosion is added thereto at about 0.3-0.5%. The iron oxide scale formed on the surface of a ferrous metal is dissolved and removed by using such soln. mixture. The washing is accomplished at a temp. of about 60-70 deg.C with the hydrochloric acid base and at about 70-85 deg.C with the sulfuric acid base. This method is adequate for the chemical surface treatment of a steam generator in a thermal power plant and a heat exchanger, etc. in a chemical plant. |
