Method for suppressing generation of nox gas in nitric acid treatment of metal

Abstract

Abstract PURPOSE:To suppress the abnormal generation of NOX and the bumping of an acid liquid caused thereby, by preliminarily adding a small amount of O3 to nitric acid additionally replenished after 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:Descaling, dissolving, coloring or polishing treatment 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, nitric acid having ozone preliminarily dissolved therein in an amount of 0.5mg or more/l nitric acid is used as nitric acid for adjustment of acid concn. added after this point of time.

Inventors

• 👤 Masayuki Hino
• 👤 肥野　真行
• 👤 Masaaki Ishikawa
• 👤 正明 石川

Bibliographic Details