Patent ID: 7353863

Claim:
A method of surface treating an aluminum alloy base body of a heat exchanger, comprising the steps of etching at least a portion of a base body of a heat exchanger comprising aluminum alloy tubes and fins with an aqueous alkaline solution having a pH value of 9.0 or more; and applying a chemical conversion treatment or a hydrophilicity-enhancing treatment to the surface of the etched base body, wherein the aluminum alloy tubes and fins of the base body are those bonded to each other by a vacuum brazing procedure in which a getting agent comprising magnesium is used to destroy an oxide layer formed on the surfaces of the aluminum alloy tubes and fins, the method further comprises a pre-treatment step in which, before the etching step is applied, an aqueous pre-treatment liquid having a pH value of 9.0 or less is brought into contact with an unclean surface of the base body to be etched.