THE EFFECT OF TEMPERATURE ON THE CORROSION BEHAVIOR OF A 70 30 CU-NI COMMERCIAL ALLOY IN SEAWATER/

A series of experiments was carried out in seawater at different tempe ratures in order to investigate the correlation between the modificati on of the composition of the passive layer linked to temperature chang e and the resistance of the alloy against generalized or localized cor rosion. Free corrosion and electrochemical tests (polarization curves, impedance measurements) were carried out at 20, 40, 60, 80-degrees-C in quiescent seawater at pH 8.2 with dissolved oxygen (D.O.) contents ranging from 6.5 ppm (at 20-degrees-C) to 3.0 ppm (at 80-degrees-C). T he corrosion products adherent to the metallic surface were analysed w ith chemical and XPS methods. It was found that by increasing the temp erature: (a) the corrosion rate of the alloy increases; (b) selective copper dissolution takes place; and (c) the nickel amount in the corro sion products increases owing to the formation of a copper-nickel oxid e, with a nickel content higher than in the alloy.