The runoff rates of copper and copper alloys CuSn9 and CuSn3Zn9 have been studied along a field exposure of one year in an urban area located in upper Normandy region in northern France. Mass measurements of samples, analysis of the adherent corrosion layers and runoff rates of metals were carried out throughout the exposure time. Runoff rates turn to be relatively stable during the exposure time. The influence of alloying elements on the copper runoff rate has been studied and it was demonstrated that addition of zinc permit to decrease the amount of copper that releases from the corroded surface by rainfall. Concerning the tin content, no significant influence has been observed on the copper runoff