A PERIODIC VOLTAGE MODULATION EFFECT ON THE CORROSION OF CU-NI ALLOY

It is suggested in the literature that the application of A.C. fields results in enhanced corrosion rates of materials while the mechanism of corrosion is changed. In this study, corrosion caused by sinusoidal alternating Voltage (A.V.) fields in Cu-10Ni alloy (CDA706) in simulated seawater is investigated by: (i) immersion tests and (ii) characterization of corrosion products. The experimental data show that under the influence of alternating voltage (60 Hz) applied between Cu-Ni ahoy and a platinum mesh counter electrode, the corrosion rate of the alloy increases with the applied voltage. It was also found that the corrosion rate of the alloy decreased with frequency and time. D.C. polarization curves revealed that passivity was insignificant in the alloy/seawater corrosion system studied. A cuprous oxide film which acts as a diffusion barrier layer to the dissolution of metals protected the alloy from corrosion. Preferred dissolution of nickel was the major anodic reaction causing pitting. The data suggest that application of A.V. signals does not change the mechanism of corrosion of Cu-Ni alloy in simulated seawater.