Use of nitrogen compounds in the pickling of stainless steel

摘要

The present invention relates to an acidic aqueous solution suitable for the pickling of stainless steel grades that comprises accelerators based on water soluble inorganic compounds comprising at least one nitrogen atom in an oxidation state in the range of −2 to −⅓. The present invention further encompasses a process for the pickling of stainless steel that makes use of a pickling solution comprising the above-mentioned accelerators.

主权项

1. An acidic aqueous solution suitable for the pickling of stainless steel comprising
a) 20 to 350 g/l calculated on a sulfate basis of at least one water soluble inorganic compound that acts as a source of sulfate anions, b) 9 to 150 g/l calculated on a fluorine basis of at least one fluorine-containing water soluble inorganic compound that acts as a source of fluoride, c) in total at least 0.01 g/l calculated on a nitrogen basis of one or more accelerators based on water soluble inorganic compounds comprising at least one nitrogen atom in an oxidation state in the range of −2 to −⅓, d) not more than 100 g/l of iron ions, wherein free sulfuric acid is present in an amount of at least 20 g/l, but not more than 200 g/l calculated on a sulfate basis; wherein free hydrofluoric acid is present in an amount of not more than 60 g/l calculated on a fluorine basis; and wherein the solution has a redox potential of at least +230 mV.