Paint Adhesion Following Deformation as Related to the Surface Structure of Hot-Dipped Galvanized Steel

The quality of the adhesion of paint to hot-dipped galvanized steel under severe deformation increases as the fraction of grains with the (0001) plane approximately parallel to the surface increases. Paint adhesion is improved by a small grain size of the zinc and by a rolling operation. The best paint adhesion has been observed on samples with a small grain size of zinc, very highly oriented with (0001) planes parallel to the surface. The fraction of grains exhibiting orientations approximating (0001) was determined by X-ray diffraction analysis and by a newly-developed etching procedure. The effect of grain orientation on paint adhesion is attributed largely to the mechanism of deformation of zinc although the chemical properties of zinc are also a function of the crystal face exposed at the surface.