| abstract |
(57) [Summary] PROBLEM TO BE SOLVED: It can be baked at a temperature of 200 to 330 ° C., the same as a dichromate-based treatment solution, using a phosphate-based treatment solution that does not contain chromium. An inorganic or semi-organic insulating film having excellent water resistance and adhesion even with a thin film of m 2 or less is formed on the surface of the electromagnetic steel sheet. SOLUTION: A phosphonic acid chelating agent is added to an aqueous solution of a polyvalent metal phosphate, the sum of the product of the number of moles of the metal atom in the polyvalent metal phosphate and its valence ΔMi, the number of moles of the chelating agent and the molecule. The ratio of the product of the number of acid groups in the product to the sum と Oi (ΣOi / ΣM Use a treatment liquid added at a ratio where i) is in the range of 0.1 to 5. The treatment liquid may further contain one or more of an aqueous synthetic resin, boric acid, and colloidal silica. |