The surface composition of phosphated galvanized steel sheets with and without chromate post rinse has been studied in order to clarify the effect of chromate treatment on wet adhesion. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses disclosed that an incomplete phosphate layer composed of dihydrate phosphate and ferric compounds (Fe 2 O 3 and FePO 4 ) was present on the surface of hopeite coatings on an as-phosphated sheet. Chromate post treatment remarkably improved the wet adhesion of full-painted sheets by: (1) removal of the incomplete layer which may dissolve during cathodic electrodeposition and (2) formation of a CrOOH compound strongly bonded to the resin due to its hydrogen bond.