| 摘要 |
PURPOSE:To make it possible to effectively suppress the remarkable generation of NOX or the bumping of an acid liquid, by preliminarily adding a small amount of H2O2 to nitric acid additionally replenished since the point of time when the amount of sulfamic acid in a nitric acid containing liquid is reduced to a proper amount or less. CONSTITUTION:Treatment such as descaling, dissolving, coloring or polishing treatments is carried out with respect to the surface of a metal in a nitric acid containing liquid to which sulfamic acid having effect for suppressing the generation of NOX is added. In this case, sulfamic acid in the nitric acid containing liquid is reduced to a proper amount or less or completely consumed during said treatment. In such a case, 0.1wt% H2O2 is preliminarily added to and dissolved in nitric acid used in adjusting acid concn. added after this point of time. By adding and replenishing this H2O2 added nitric acid, the abnormal generation of NOX and the bumping of the nitric acid containing liquid caused thereby can be suppressed. |
