Improvement of the compatibility between phosphating film and coating in the pretreatment of automobile coating

The compatibility of phosphating film and coating has become a very concerned problem With the development of coating technology, higher requirements are put forward for the matching of phosphating treatment and coating In the past, too much emphasis has been placed on the corrosion resistance of phosphating film itself, while the compatibility between phosphating and coating has been neglected In fact, the phosphating film itself does not bear much corrosion resistance in the whole coating system The key is the good matching between phosphating film and coating, which is particularly important for electrophoretic coating Especially at present, some township enterprises have built or prepared to build cathodic electrophoresis production line, so improving the matching of phosphating film and cathodic electrophoresis coating has become a new research topic for coating enterprises The way to improve the compatibility of phosphating film and cathodic electrophoretic coating is to improve the alkali resistance of phosphating film, that is, the higher the alkali resistance, the less the phosphating film dissolves in the process of cathodic electrophoretic film formation, and the higher the quality of cathodic electrophoretic coating This requires not only a dense phosphating crystal, but also a high P ratio (more than 85%) To improve the P ratio, commonly used manganese containing low zinc phosphating, ultrasonic phosphating, phosphating film passivation treatment, etc.