Study On Semi-Organic Chromium-Free Insulating Coating Based On Epoxy Resin

Non oriented silicon steel is widely used in electric power,electronic and military industry.In order to reduce the loss,it needs to be coated with insulating coating on its surface.The main filler of traditional non-oriented silicon steel coating is chromate,and it is facing severe environmental pressure during the coating preparation and solid waste management.At present,western developed countries have banned the use of chromium in insulating coating of non oriented silicon steel.Due to technical reasons,our country is still in the extensive use of chromium coating.As the leading major steel plants and research institutes,Shanghai Baosteel and Wuhan Iron and Steel have launched a researching of coating liquid composition and preparation of non chromate insulating coating,but there is a certain gap with chromium coating in adhesion,heat resistance and etc.In this paper,we studyed the method of chromium-free insulating coating of non-oriented silicon steel and analyzed the effects of main components on the adhesion and heat resistance of the coating by epoxy resin,phosphate,titanium chelate,cobalt hydroxide,strontium hydroxide as the basic component,and aluminum silicate,boric acid and sodium tungstate as modified filler.The main conclusions are as follows:(1)With 10.9%epoxy resin and 26.1%phosphate as the main ingredient,the cobalt hydroxide 0.9%and strontium hydroxide(1:1),aluminum silicate and titanium chelate 1.3%0.2%as additives,we successfully prepared the semi organic chromium-free insulating coating of non-oriented silicon steel which have good adhesion and heat resistant temperature of 580? after 360? insulation 60s baking.When the content of titanium chelate increased,the heat resistance of the coating decreased obviously.(2)The baking temperature had a significant effect on the heat resistance of the insulating coating,and the heat resistance of the coating was higher in the range of 360 to 530?,which was lower than 320?.The corrosion resistance increased,heat resistance decreased and the chang of adhesion not obvious,when epoxy resin content increased from 10.9%to 20.9%.(3)Adding appropriate amount of aluminum silicate and boric acid can obviously improve the heat resistance of the coating.The optimum content of aluminum silicate was 0.3%,and the optimum content of boric acid was 3.5%to 6.5%.The highest heat resistance of coating can reach 750 degree heat insulation 2h after composition optimization.On the basis of adding 3.5%boric acid,adding 0.9 to 1.8%sodium tungstate,can improve the corrosion resistance of the coating and keep the heat resistance unchanged at the same time.