The Function of Cobalt Oxide in Ground Coat
Cobalt oxide is a very important component in the enamel ground coat. Because of its high raw material price, the price of cobalt oxide has a greater impact on the cost of enamel, although its addition is usually not large.
In order to strengthen the adhesion between the ground coat and steel, a blue ground coat containing 0.3 to 0.6% of Cobalt oxide is usually used, and 1.5% of manganese oxide and 0.4% of nickel oxide are added to enhance the adhesion. However, when all these oxides replace the Cobalt oxide, the adhesion will be reduced.
There are many reasons why a small amount of Cobalt oxide promote the adhesion of ground coat and steel plate.
1. Enamel frit with Cobalt oxide can corrode the steel surface and cause the surface to be rough, thus strengthening the adhesion between the enamel and the steel plate.
2. During firing, a little iron oxide melts and enters the ground coat. If the ground coat contains Cobalt oxide, its melting concentration can be controlled to produce the best conditions for the ground coat to be tightly bonded to the steel plate.