Method for preparing cerium-manganese/molybdenum multi-element composite conversion coating on surface of aluminum alloy

The invention discloses a method for preparing a cerium-manganese/molybdenum multi-element composite conversion coating on the surface of aluminum alloy. The method comprises the following steps of: (1) pretreating and activating the aluminum alloy; and (2) placing the aluminum alloy treated in the step (1) in Ce-Mn conditioning fluid so as to prepare the golden cerium-manganese conversion coating on the surface of the aluminum alloy; and (3) placing the aluminum alloy treated in the step (2) in Mo-containing conditioning fluid to obtain the cerium-manganese/molybdenum multi-element composite conversion coating. The conditioning fluids adopted in the method do not contain toxic substances. The multi-element composite conversion coating with excellent corrosion resistance and weather resistance as well as relatively good wear resistance can be prepared on the surface of aluminum alloy. The method is relatively simple in technology, simple and convenient to operate, low in cost and easy to industrialize.