Abstract
The purpose of this paper is to find out suitable conditions for obtaining stable zinc phosphate film on Al, Fe and Zn surfaces by controlling the composition of the zinc phosphating bath. The Taguchi method was employed to analyze the effect of control factors. It was revealed that the increase of zinc ion concentration in the bath exerted the most significant effect on the increase of crystal grain size and the average weight of zinc phosphate films. The F ion was effective in controlling the S/N ratio of aluminum alloy sheets. Corrosion resistance and paint adhesiveness were evaluated using painted panels which were pretreated simultaneously under suitable conditions. The 5xxx series aluminum alloy and steel sheets showed almost the same paintability and 6xxx series aluminum alloy showed slightly a poorer corrosion resistance compared with steel sheets.