ELECTROMAGNETIC STEEL SHEET WITH INSULATING FILM AND TREATMENT LIQUID FOR FORMING THE INSULATING FILM

摘要

PROBLEM TO BE SOLVED: To form an insulating film on a surface of an electromagnetic steel sheet without using chromium or boric acid potentially causing environmental problems, wherein the insulating film does not undergo whitening and shows high adhesion.SOLUTION: An aqueous treatment liquid for forming an insulating film comprises: primary phosphate of a polyvalent metal essentially comprising Al and/or Mg; and in terms of solid content, based on 100 pts.mass of phosphate, 5 to 50 pts.mass of nitric acid compound chosen from nitric acid and polyvalent metal nitrate; and 5 to 100 pts.mass of chelating agent chosen from a phosphonic acid compound and pyrophosphoric acid. The aqueous treatment liquid may further comprise, based on 100 pts.mass of phosphate, 5 to 50 pts.mass of polyvalent metal hydroxide (preferably Sr hydroxide) and 3 to 100 pts.mass of aqueous resin.