| 摘要 |
PURPOSE:To remove selectively only strippable oxide scale by using a relatively mild org. acid to remove oxide scale formed by the contact of Cr alloy steel with steam. CONSTITUTION:An aqueous soln. contg. 0.5-10% org. acid and 0.3-1.0% corrosion inhibitor is heated to 50-90 deg.C, and a pipe 1 or the like of Cr alloy steel having oxide scale formed by contact with steam is washed with the aqueous soln. The oxide scale consists of the 1st Cr-rich, hard and dense layer 2 with low strippability and the 2nd Fe-rich and relatively porous layer 3 with high strippability. Thus, only the layer 3 which is liable to be stripped can be dissolved and removed without dissolving the layer 2 which protects well the pipe 1 from steam oxidation. |
