Corrosion Behavior of 70Cu-30Ni Alloy in 0.5M NaCl and in Synthetic Seawater

Abstract

Abstract Electrochemical corrosion rates of 70Cu-30Ni alloy have been measured in oxygenated 0.5M NaCl and in synthetic seawater by the Tafel extrapolation procedure using a rotating disk electrode system. The rotation rate was varied from 500 to 6000 rpm. A log-log plot of the corrosion current vs rotation rate was linear, with a slope of 1/6 for the alloy in 0.5M NaCl; the corrosion potential for the same system became more negative at a rate of approximately −20 mV/dec of rotation. The anodic partial currents at potentials close to the corrosion potential in 0.5M NaCl increased linearly with the square root of the rotation rate. Corrosion current and corrosion potential as well as the anodic partial current for the alloy in synthetic seawater remain unchanged with rotation rate. The anodic Tafel slopes were 60 and 90 mV in 0.5M NaCl and synthetic seawater, respectively. The cathodic Tafel slope was 200 mV for both systems. Two separate corrosion mechanisms for the alloy in two electrolytes have been re...