Aluminum surface having chemical conversion coating formed by reaction of nitrate/sulphate and organic compound

摘要

A chemical conversion coating formed on a surface of an aluminum substrate comprises a composite material formed by a reaction of a nitrate or sulphate of an alkali metal or alkaline earth metal and an organic compound that can form a compound with aluminum or exhibit a weak basicity in an aqueous aluminum treating liquid comprising the nitrate or sulphate of alkali metal or alkaline earth metal and the organic compound, with the aluminum substrate. The coating is corrosion-resistant, bacteria-proof or fungiproof, and the surface may be of a heat exchanger. The organic compound may be sodium mercaptobenzothiazole, oxine triethanolamine or sodium benzoate. The conversion coating consists of a basic double salt including aluminium ions, at least one metal ion selected from alkali metal ions or alkaline earth metal ions. at least one ion selected from nitrate and sulphate ion, and an ion derived from the organic compound.