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 sup erimposition of alternating voltages was Found to occur via intergranu lar corrosion and cracking mechanisms, as evidenced by scanning electr on microscopy. Experiments were conducted at three different DC potent ials on which sinusoidal full-wave, positive half-wave rectified and n egative half-wave voltages were superimposed under nitrogen or air pur ge. Evidence of significant material degradation was found even when n egative 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 corros ion 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.