Electromagnetic steel sheet having a highly corrosion-resistant insulating film and a core for use in motors or transformers made of the electromagnetic steel sheet

摘要

An electromagnetic steel sheet having a corrosion-resistant electrically insulating film. The insulating film is formed by spraying and baking, on the steel sheet, a treating liquid containing an emulsion of fine resin particles, a reducing agent and an accelerator. The emulsion of fine resin particles exhibits a weight change peak temperature of not lower than about 400 DEG C as measured by differential thermal weight measurement conducted while raising the emulsion temperature at a constant rate of temperature rise. The emulsion also substantially resists when contacted by phosphoric acid. The reducing agent is a phosphate ion aqueous solution containing a metal. Also disclosed is a corrosion-resistant core made from the electromagnetic steel sheet.