TREATING LIQUID FOR SURFACE TREATMENT OF ALUMINUM OR MAGNESIUM BASED METAL AND METHOD OF SURFACE TREATMENT

摘要

A method of surface treatment which comprises contacting aluminum, an aluminum ally, magnesium or a magnesium alloy with a treating liquid comprising (1) a compound (A) containing at least one metal atom of Hf(IV), Ti(IV) and Zr(IV), (2) a fluorine-containing compound in an amount sufficient for causing fluorine to be present in the treating liquid in a molar concentration which is at least five times that of the total metal contained in the compound A, (3) at least one metal ion (B) selected from the group of alkaline earth metals, (4) at least one metal ion (C) selected from the group consisting of Al, Zn, Mg, Mn and Cu, and (5) a nitrate ion, wherein the compound (A) is present in a molar concentration of 0.1 to 50 mmol/L in terms of the at least one metal atom of Hf(IV), Ti(IV) and Zr(IV). The method allows the formation of a surface treatment coating excellent in the corrosion resistance in both a bare state and a painted state, without the production of wastes such as a sludge and without the use of a harmful component.