Treating a silicon steel material having a silicate protective coating thereon with an aqueous solution containing phosphates to form a further protective coating
AssigneeASEA Aktiebolag
InventorCarl Artur Akerblom
Life of this patent
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Abstract
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.degree. C, and then heated to temperatures of between about 400.degree. and 1100.degree. C for periods of between about 1/2 minute to 10 minutes in order to form a further protective phosphate layer.
Claims16
A process for reinforcing a silicon steel material which has an alkaline earth metal silicate protective layer thereon comprising the steps of coating the alkaline earth metal silicate protective layer with an aqueous solution containing colloidal or suspended silica;
- 10-200 parts by weight phosphate ions, based on 100 parts by weight of silica calculated as SiO.sub.2 without water;
- 2-20 parts by weight of ions selected from the group consisting of iron and manganese ions, or both;
- and an amount of negative ions which deviates from an equivalent amount of hydrogen ions in the solution by a maximum of 40 percent and which are capable of converting to volatile products at temperatures of below 400.degree. C;
- and then heating the coated silicon steel material to form a further protective phosphate layer over the alkaline earth metal silicate protective layer.
Dependencies are inferred from the claim text.