A Study to Determine the Mechanisms of Corrosion of Copper-Nickel Alloys in Sulfide-Polluted Seawater.
Annual rept. 2 Feb 77-1 Feb 78,
SRI INTERNATIONAL MENLO PARK CA
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The corrosion of 9010 CuNi and 7030 CuNi alloys in flowing seawater 1.62 ms has been studied as a function of oxygen concentration using the linear polarization, ac impedance, and potential step methods for measuring the polarization resistance. Satisfactory agreement is obtained between these three semicontinuous techniques and measurements of weight loss, thereby demonstrating the suitability of electrochemical methods for monitoring the corrosion rate of cupronickel alloys in seawater. The high-nickel alloy is found to be more corrosion resistant than the 9010 CuNi alloy under the conditions employed, provided that O2 or 6.60 mg1. In oxygen-saturated seawater, the superior behavior of the 7030 CuNi alloy is no longer observed. The loss in corrosion resistance of the 7030 CuNi alloy is correlated with a shift in the corrosion potential, to a value more noble than the break-away potential defined here as the potential at which a sudden increase in anodic current occurs on sweeping the potential in the active to noble direction.
- Properties of Metals and Alloys
- Marine Engineering