METHOD FOR PICKLING NICKEL-BASE STAINLESS STEEL SHEET

PURPOSE:To enable the pickling of Ni-base stainless by sulfuric acid at a low cost, in Ni-base stainless, by enabling its whitening treatment after pickling by sulfuric acid. CONSTITUTION:An Ni-base stainless steel sheet is pickled by sulfuric acid. After that, the surface of the steel sheet is subjected to cleaning treatment by a whitening pickling soln. having 0.5 to 20wt.%. hydrochloric acid concn. and 3 to 20wt.% nitric acid concn., and thereafter, washing treatment is executed. The whitening pickling soln. furthermore may contain a surfactant constituted of a urea compound and organic acid by 1 to 5wt.%. In this way, the pickling of Ni-base stainless is made possible, and remarkable effects such as the reduction of equipment and building cost, the reduction of acid soln. running cost, the elimination of nitric and hydrofluoric acid sludge treatment, the evasion of the risk to hydrofluoric acid, the reduction of equipment maintenance cost or the like are given. Moreover, in a line in which both of Cr and Ni-base stainless are produced, the equipment, operating time and cost required for the change of the son. are made needless.