Method for pickling mettalic surface, pickling solutions therefor, and process for regenerating spent pickling solutions

摘要

A method for removing scales formed on iron-based metal alloy containing Ni and/or Cr comprising contacting the metal alloy with a pickling solution containing nitrates and fluorides as essential components. The nitrates and fluorides used for the method are superior to the mixture of nitric acid and hydrofluoric acid in pickling efficiency, fundamental elimination of noxious gas; and optional abbreviation of pre-treatment before pickling. The pickling solution may also contain auxiliary component. A pickling composition containing nitrates and fluorides and a regenerating method of spent pickling solution is also provided.