FORMATION OF COLORLESS CHROMATE FILM ON ALUMINUM WHEEL

摘要

PURPOSE: To provide the formation of a colorless chromate film on an aluminum wheel, by which brightness of the aluminum wheel base material can be maintained and the aluminum wheel having excellent corrosion resistance (partic ularly filiform corrosion resistance) and adhesion after coating, can be obtained. ;CONSTITUTION: The formation of the colorless chromate film on an aluminum wheel features in that the aluminum wheel is dipped in an acidic aqueous solution, which contains ≥2g/1 hexavalent chromium ion, 20 to 2000ppm sulfate ion and 10 to 400ppm fluorine and the pH of which is 0.6 to 1.7, and then completely sunk into the above acidic aqueous solution and thereafter subjected to cathode electrolysis treatment with a 0.5 to 15A/dm² current density for ≥4 sec and then taken out from the acidic aqueous solution after a time of 1 to 300sec elapses from the point when the current being made to flow through the solution is stopped. Thus, the aluminum wheel having particularly improved filiform corrosion resistance can be obtained.;COPYRIGHT: (C)1995,JPO