1991 Volume 77 Issue 3 Pages 414-421
In the previous papers, we examined the effects of phosphate and silica in chromate films on the performance of a chromate-treated electro-galvanized steels, and found that required properties except paint adhesion were improved by those elements. In this paper, we examined a small addition of water-soluble resin to phosphate-silica-chromate solution for improving the paint adhesion.
It was found that the addition of resin less than 1.0mg/m2 enhances wet and dry adhesion of the paint remarkably, but adding an excess amount of resin deteriorates corrosion resistance of the chromate film.
The role of the resin in the improvement of the paint adhesion was considered to be as follows ;
The resin tends to be concentrated to the film surface and conceal polar elements such as silica and zinc phosphate. As a result, the hydrogen bonding force of surface tension of the chromate film is kept moderate, and the wet adhesion was improved. Instead, the dispersion force component of surface tension is increased by resin addition, which improves the dry paint adhesion.
