Effect of heat treatments on Cu‐Ni 70/30 alloy pitting susceptibility in sea water at different temperatures

摘要

AbstractA series of experiments was carried out on Cu‐Ni 70/30 commercial alloy specimens presenting different microstructures. The microstructure of homogeneized specimens was modified with annealing treatments by which grain size significantly increased and intermetallic compounds precipitated, thus creating some dishomogeneity in the alloy.Free corrosion and electrochemical tests were carried out at 20, 40, 60, 80°C in quiescent sea water at pH 8.2 with dissolved oxygen (D.O) content ranging from 6.5 ppm (at 20°C) to 3.0 ppm (at 80°C). The corrosion products adherent to the metallic surface were analyzed with chemical and XPS methods.The following could be observed:with increasing temperature, a decrease in corrosion rate and selective copper dissolution was observed in homogeneized and annealed specimensthe annealed specimens have the highest corrosion rate in the whole temperature range and undergo pitting corrosion at low tempera