亜鉛めっき鋼板上へのリン酸アルミニウム熱重合体皮膜の形成について

抄録

A new chemical conversion coating process using aluminum biphosphate has been proposed, and the film formation behavior and mechanism of thermally polymerized aluminum phosphate have been studied. The chemical conversion film formed by heating the aluminum biphosphate coating on zinc-plated steel sheets provides good protection against corrosion. Reaction for the film formation is a condensation polymerization caused by the dehydration of bound water in aluminum biphosphate. The experimental results obtained by using DSC, TGA, IR spectrometry and X-ray diffractometry showed that the dehydration at about 150°C is most important to form the anticorrosive film. Accordingly, for the production of the chemically converted film it is required to heat up to at least about 180°C, at which most of the dehydration reaction ends. However, the dehydration and hydration of the film occured reversibly. The reason for this rehydration is assumed that thermally polymerized film possesses a non-stoichiometrical aluminum phosphate structure.