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 0.2W2% to a hydrochloric acid or sulfuric acid alone or a soln. mixture thereof about 3W7% concn. A reducing agent composed of ≥1 kind of an L-ascorbic acid and erythorbic acid is added at about 0.1W0.3% to said soln. with respect to a 0.5W2% concn. range of the thioglycolic acid and an inhibitor for acid corrosion is added thereto at about 0.3W0.5%. 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 60W70°C with the hydrochloric acid base and at about 70W85°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.
FURUSAWA TAKETOSHI
KUDOU YOSHIO
| JPS5033933A | 1975-04-02 | |||
| JPS5753873A | 1982-03-31 | |||
| JPS5732718A | 1982-02-22 |