Electrochemistry of non-aged copper-nickel (UNS C70610) in fully developed fluid flows. Part 2: Cyclic voltammetry and the corrosion mechanism

The cyclic voltammetry and mixed potential behaviour of freshly polished UNS C70610 (CN 102) 90–10 copper–nickel has been examined in fully characterised seawaters using the rotating disc electrode (RDE) and the rotating cylinder electrode (RCE). Reynolds number dependent corrosion potentials are derived for a wide range of Reynolds numbers and good comparison is made with directly measured values. The films formed on initial exposure of the 90–10 copper–nickel alloy to the seawaters did not confer any additional protection relative to unalloyed copper. Indeed, the 90–10 copper–nickel tended to exhibit relatively high anodic and cathodic currents when directly compared to both unalloyed copper and a nickel aluminium bronze under identical conditions. The corrosion potential of the alloy becomes more negative at higher flow velocity, due to the influence of mass transport on the anodic reaction mechanism at potentials close to the mixed potential. Overall, the results indicate that the character of the freshly polished material/electrolyte interface has a much greater influence over the magnitude of the corrosion rate than the turbulence intensity of the fluid