Process for phosphate-permanganate conversion coating of Mg alloy

An orthogonal design with four factors and three levels for phosphate-permanganate conversion coating of Mg alloy was performed based on the composition of Phosphate-permanganate conversion solution consisting of KMnO4, K2HPO4, H3PO4 (adjusting pH values). It was found that the H3PO4 (pH value) is dominant in micro-conversion solution, next to K2HPO4 and KMnO4, through analyzing thickness of the conversion film and thickness adhesion. And the optimized factors was obtained, so the optimization composition proportion of the phosphate-permanganate and its process were given. The experimental results showed that the corrosion resistance is equivalent to that of conversion coating in DOW1 solution.