This study examines the corrosion behavior of aluminum alloys in condensed water containing different concentrations of anions for a heat exchanger in an automotive exhaust gas recirculation (EGR) system of a diesel engine. Electrochemical measurements and bulk analyses revealed that the aluminum alloy is protected by the adsorption of increased nitrite and nitrate ions contained in condensed water, despite increased detrimental sulfate ions at high EGR rates. The mechanism of the beneficial anions, which are nitrite and nitrate on aluminum alloy in condensed water, was spontaneous physical adsorption (physisorption).