EFFECT OF HEAT-TREATMENTS ON CU-NI 70 30-ALLOY PITTING SUSCEPTIBILITYIN SEA-WATER AT DIFFERENT TEMPERATURES/

A series of experiments was carried out on Cu-Ni 70/30 commercial allo y specimens presenting different microstructures. The microstructure o f homogeneized specimens was modified with annealing treatments by whi ch grain size significantly increased and intermetallic compounds prec ipitated, thus creating some dishomogeneitp in the alloy. Free corrosi on and electrochemical tests were carried out at 20, 40, 60, 80 degree s C in quiescent sea water at pH 8.2 with dissolved oxygen (D.O) conte nt ranging from 6.5 ppm (at 20 degrees C) to 3.0 ppm (at 80 degrees C) . The corrosion products adherent to the metallic surface were analyze d with chemical and XPS methods. The following could be observed: - wi th increasing temperature, a decrease in corrosion rate and selective copper dissolution was observed in homogeneized and annealed specimens - the annealed specimens have the highest corrosion rate in the whole temperature range and undergo pitting corrosion at low temperature.