Effect of rare earth element Y addition on the corrosion resistance of Cu-12.5Ni-5Sn alloy after aging

Abstract

Cu-12.5Ni-5Sn-xY alloy with different rare earth Y contents was prepared by spark plasma sintering (SPS). The samples underwent aging at approximately 400°C for 4 hours in an energy-saving box furnace. The effect of trace Y addition on the microstructure and corrosion behavior of aging treated Cu-12.5Ni-5Sn-xY alloy were investigated by electrochemical test, and the corrosion mechanism of the alloy was discussed. The results indicated that the addition of rare earth Y improved the uniformity of microstructure and grain size of the alloy, and improved the corrosion resistance of the alloy. When the Y content changed between 0 wt% and 1.0 wt%, the corrosion resistance of the Cu-12.5Ni-5Sn-xY alloy gradually improved. The Cu-12.5Ni-5Sn-1.0Y alloy had a lower self-corrosion current density (1.490×10−5A/cm2) and a lower corrosion rate (0.178 mm/a). Compared to the Cu-12.5Ni-5Sn alloy without Y addition, the maximum corrosion depth was reduced by about 44.6 % and the corrosion resistance was improved. Rare earth Y promoted the uniform distribution of Ni elements, inhibited the conversion of Cu2O to Cu2(OH)3Cl, enhanced the layer density and stability. The internal corrosion layer mainly consisted of NiO, the intermediate layer mainly consisted of SnO, and the surface layer mainly comprised of CuO, Cu2O, and Cu2(OH)3Cl. Additionally, Y2O3 formed on the alloy's surface, effectively prevented corrosive ion attack and enhanced the corrosion resistance of Cu-12.5Ni-5Sn alloy.