Abstract: A method for manufacturing a heat exchanger includes preparing heat exchange tubes by using an aluminum extrudate made of an alloy containing Mn (0.1 to 0.3 mass %), and Cu (0.4 to 0.5 mass %), the balance being Al and unavoidable impurities; preparing fins by using an aluminum bare material made of an alloy containing Mn (1.0 to 1.5 mass %) and Zn (1.2 to 1.8 mass %), the balance being Al and unavoidable impurities; causing Zn, Si, and flux powders to adhere to the outer surfaces of the heat exchange tubes such that the Zn powder adhesion amount becomes 2 to 3 g/m2, the Si powder adhesion amount becomes 3 to 6 g/m2, and the flux powder adhesion amount becomes 6 to 24 g/m2; and brazing the heat exchange tubes and the fins together by utilizing the Si powder and the flux powder adhered to the outer surfaces of the heat exchange tubes.

Abstract: A heat exchanger includes exchange tubes formed from an aluminum extrudate and fins made of an aluminum bare material. The wall of each heat exchange tube is composed of a main body portion made of an Al alloy forming the aluminum extrudate, and a covering layer made of an Al—Si—Zn alloy and covering the main body portion. A diffusion layer containing Zn and Si diffused from the Al—Si—Zn alloy is formed in an outer surface layer portion of the main body portion. A low potential portion whose spontaneous potential is the lowest, and a high potential portion whose spontaneous potential is 60 mV or more higher than that of the low potential portion, are present within a range between an outermost surface of the wall and a deepest portion of the diffusion layer such that the low potential portion is located toward the outermost surface of the wall.

Abstract: The wall of each heat exchange tube of a condenser for a car air conditioner is composed of a core material layer, a first brazing material layer covering the outer surface of the core material layer, and a second brazing material layer covering the inner surface of the core material layer. A Zn diffused layer is formed in an outer surface layer portion of the core material layer. The deepest portion of the Zn diffused layer is located at a position 70 to 100 ?m deep from an outermost surface of the wall. The Zn concentration of the outermost surface of the wall of the heat exchange tube is 0.55 mass % or higher. The Zn diffused layer includes a high potential portion whose spontaneous potential is at least 41 mV higher than the spontaneous potential at the boundary between the core material layer and the first brazing material layer.