Orthogonal Optimumization of Technological Parameters for Preparation of Lanthanum Conversion Film on 6061 Aluminum Alloy

Take the thickness of conversion film and spot test time as assessment criteria, the optimal formula and technological parameters of conversion processing solution with La(NO3)3·6H2O and KMnO4 as additives were obtained as follows: La(NO3)3·6H2O 15 g·L-1, KMnO4 4 g·L-1, (40±2) ℃, 10 min, pH=3.5. The conversion film formed under the technological conditions has good corrosion resistance. And the corrosion rates of conversion film prepared with optimum process parameters and aluminum alloy in 3.5% NaCl solution were compared. The results show that rare earth conversion film on aluminum alloy can reduce the corrosion rate of 6061 aluminum alloy, and thus improve the corrosion resistance of aluminum alloy matrix.