The corrosion of Cu-Ni alloy in a chloride solution subjected to periodic voltage modulation: Part II

The corrosion of samples of CDA 706 copper-nickel alloy due to the superimposition of alternating voltages was Found to occur via intergranular corrosion and cracking mechanisms, as evidenced by scanning electron microscopy. Experiments were conducted at three different DC potentials on which sinusoidal full-wave, positive half-wave rectified and negative half-wave voltages were superimposed under nitrogen or air purge. Evidence of significant material degradation was found even when negative half-wave rectified sinusoidal voltages were superimposed upon the test coupons. The extent of surface damage suffered by specimens was found to decrease with frequency of the applied signal. The corrosion products formed on the samples, as determined by energy-dispersive X-ray analysis, contain it significant presence of chloride. A strong correlation between the pH of the solution and metal dissolution rate is observed. A possible reaction pathway for the corrosion mechanism is suggested. (C) 1998 Elsevier Science Ltd. All rights reserved.