Discussion on the film-forming mechanism of ceramic chemicals

In the production process of the household appliance industry, the base material of the parts is mostly cold-rolled sheet. In the stamping process, stamping oil or drawing oil is often used to make the smooth surface with oil stains. If not treated, it will affect the performance of the subsequent spraying coating. Phosphating is a traditional process widely used for metal surface pretreatment. Phosphate chemical conversion film (phosphating film for short) is formed on the surface of metal substrate through chemical reaction between phosphate and metal substrate, which plays a role in reducing the surface activity of metal substrate and improving the surface corrosion resistance.

Phosphating technology has been developed for more than one hundred years and has been widely used in various industrial fields such as automobiles, household appliances, machinery, etc. It has played a very important role in the process of social and economic development. However, as people pay more attention to environmental protection and the environmental protection requirements become higher and higher, the disadvantages of phosphating technology become more and more prominent, and new environment-friendly phosphorus-free pretreatment products emerge as the times require.

1. Ceramic film forming mechanism

The ceramic agent technology is divided into two steps:

Zirconium fluoride is hydrolyzed to form zirconia sol (ZrO2 can be dissolved in its aqueous solution to form a sol under low pH conditions) (H2ZrF6+H2O → ZrO2+HFb) The treated metal substrate is dissolved in the acidic system of the zirconium salt treatment solution, and the electrochemical reaction occurs on the surface of the metal substrate, resulting in an increase in the pH value of the micro-negative zone, and ZrO2 is deposited on the surface of the metal substrate under high pH conditions.

The nano ceramic chemical conversion film with dense structure deposited on the surface of metal substrate has strong resistance and good adhesion with metal oxide and subsequent organic coating, which can significantly improve the corrosion resistance of metal coating.

2. Application process of ceramic agent technology

Based on the significant advantages in terms of use cost and environmental protection, ceramic technology is increasingly favored by household appliance manufacturers. Manufacturers using traditional phosphating process have begun to carry out the transformation of phosphating line. The new production line also chooses phosphorus-free pretreatment technology due to the cost and environmental pressure. The process determined in the process of switching between the old line and the new line will be different, as shown in the following table.

Compared with the traditional phosphating pre-treatment process, the original surface conditioning process is changed to water washing when the old line is switched, which enhances the cleaning before vitrification; The new production line saves the surface adjustment process, saves the equipment investment and improves the production rhythm. At the same time, for conditional production lines, equipped with a pure water system can improve the quality of ceramic film and prolong the service life of the tank liquid.