Patent ID: 9416454
Filing Date: 2016-08-16
CPC Classification: C23C,C23G

Claim Text:
1. A method for conversion treating surface of a magnesium alloy workpiece comprising: providing a magnesium alloy workpiece; placing the magnesium alloy workpiece in a degreasing solution to remove oil from a surface thereof; placing the magnesium alloy workpiece in an acid pickling solution in a first acid pickling treatment step to remove oxides, release agent, dirt and magnesium granules left behind in cold working adhered on the surface thereof; placing the magnesium alloy workpiece in a surface conditioning solution in a first surface conditioning treatment step to remove residues adhered on the surface thereof after the first acid pickling treatment step; placing the magnesium alloy workpiece in the acid pickling solution in a second acid pickling treatment step to further remove oxides, release agent, dirt and magnesium granules left behind in cold working adhered on the surface thereof; placing the magnesium alloy workpiece in the surface conditioning solution in a second surface conditioning treatment step to remove residues adhered on the surface thereof after the second acid pickling treatment step; placing the magnesium alloy workpiece in a pre-phosphating solution in a pre-phosphating treatment step to neutralize a residual solution on the surface thereof after the second surface conditioning treatment step; placing the magnesium alloy workpiece in a phosphating solution in a phosphating treatment step to form a phosphating film on the surface thereof; wherein the phosphating solution comprises phosphoric acid, manganese phosphate acid, calcium dihydrogen phosphate, sodium zirconate, sodium vanadate, and sodium molybdate, and sodium silicate.