Treating a silicon steel material having a silicate protective coating thereon with an aqueous solution containing phosphates to form a further protective coating

摘要

Silicon steel sheets which have a silicate protective coating are further protected by being first coated with an aqueous solution containing (1) phosphate ions, (2) silica grains, (3) iron and/or manganese ions, and (4) negative ions which convert to volatile products at temperatures below 400 C, and then heated to temperatures of between about 400 and 1100 C for periods of between about 1/2 minute to 10 minutes in order to form a further protective phosphate layer.