As a method of surface treatment of aluminum and/or aluminum alloy, there is known chromate treatment, and zirconium phosphate treatment (cf. Japanese Kokai Publication Hei-05-302042, for instance). However, since chromate treatment uses harmful chromium metal, it causes a problem of liquid waste treatment. In zirconium phosphate treatment, there is a problem of being low in corrosion resistance.
Further, though surface treating agents which use a fluorine and zirconium-containing compound are used, there may be cases where the corrosion resistance is inadequate in some uses even though using such surface treating agents. Therefore, a rust prevention coating agent is desired, which can impart higher corrosion resistance to aluminum and/or aluminum alloy. As such a rust prevention coating agent, there has been disclosed a surface treating agent, which contains a zirconium compound and a compound containing nitrogen atoms having a lone pair (cf. Japanese Kokai Publication 2000-204485, for instance). But, adequate corrosion resistance has not been attained even though using such a surface treating agent. And, coats obtained by using such a surface treating agent were inadequate for being adopted as a rust-proofing because they have low corrosion resistance during not yet being coated and insufficient adhesion to a coating film.