Abstract: Disclosed are methods for coating aluminum alloy heat exchangers that include the use of a waterborne top coating. By using a waterborne top coating, relative to a solvent borne, useful advantages can be achieved, such as improved penetration depth of the top coating. An example method includes cleaning a surface of a heat exchanger; contacting the surface of the heat exchanger with a first mixture to provide a passivation layer on the surface of the heat exchanger; contacting the passivation layer with a second mixture in a bath and applying a positive charge to the bath to provide an electro-coating on a surface of the passivation layer; and contacting the electro-coating with a third mixture, the third mixture including water and a polymer resin having anti-corrosion and ultraviolet protection properties, to provide a top coating including the polymer resin on a surface of the electro-coating.