To provide a chromate treatment method featuring an excellent adhesion property to coating materials and a process for producing steel products to be coated which have the excellent adhesion property to the coating materials.
A chromate treating agent prepd. by dispersing gaseous phase silica into an aq. chromic acid soln. subjected to partial reduction and further, adding metal ions having the precipitation pH value of hydroxide more on the acidic side within 2 than the isoelectric point pH value of the chromate layer and the pigments added to an org. resin layer which is the upper layer thereof at 10-5 to 10p-3 in the molar ratio to the quantity of the gaseous phase silica is applied on the steel products as a surface prepn. treatment, by which the surface prepn. treatment to form the chromate layer is executed.
WAKAMATSU TOMIO
OGISHI HIDEO
