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

A composition for surface treatment of aluminium, aluminum alloy, magnesium or magnesium alloy and the treating solutions being diluted to the desired concentration are defined. A said composition of this invention containing (1) compound A containing at least one metal element selected from the group consisting of Hf(IV), Ti(IV) and Zr(IV), (2) fluorine containing compound of sufficient amount to make fluorine existed in the composition at least by 5 times of molarity to the total molarity of metal contained in above mentioned 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) nitric ion and the mol concentration of compound A is 0.1-50 mmol/L as metal element of Hf(IV), Ti(IV) and Zr(IV). The metal treated with the treating method applying the present invention solution has excellent resistance to various corrosive environments.