Corrosion behavior of heat-treated nickel-aluminum bronze and manganese-aluminum bronze in natural waters

Abstract

Nickel aluminum bronze (NAB) and manganese aluminum bronze (MAB) are highly alloyed bronzes that are increasingly employed in several industrial sectors mainly related to the hostile environment due to their excellent resistance against corrosion, cavitation, erosion, and improved mechanical properties in comparison with other copper-based alloys. These materials are sensitive to thermal treatments, such as welding, due to a multiphase microstructure in cast conditions. To contribute to the knowledge of the behavior of both alloys, the effect of welding processes on the corrosion behavior of NAB (CuAl10Fe5Ni5) and MAB (CuMn12Al8Fe4Ni2) is studied. As the microstructures of the parent zone (PZ), heat-affected zone (HAZ), and weld seam (WS) may be quite different, the consequences with respect to corrosion behavior must be considered. In this study, the influence on corrosion behavior in synthetic sea water (SSW) was investigated using different welded test coupons representing identical (symmetrical) and hybrid joints of NAB and MAB. The microstructures of the welded samples were characterized by metallography using two chemical agents and examined by optical and scanning electron microscopy. By electrochemical corrosion testing, the major effect of welding processes on the corrosion behavior was found in influencing the amount and distribution of β-phase which is prone to selective corrosion.