On the critical flow velocity for erosion-corrosion of Cu-Ni alloy BFe30-1-1 in artificial sea water

The erosion-corrosion behavior of the copper-nickel alloy BFe30-1-1 in artificial sea water with different fluid velocities has been studied by using a rotating cylinder apparatus. The methods adopted in the experiment were weight-loss test, linear and cycle polarization, free corrosion potential and electrochemical impedance spectrum (EIS) measurements as well as SEM observation and EDX analysis. The major emphasis of the study was placed on the critical flow velocity. The results showed that the constant of linear polarization for the corrosion reaction of BFe30-1-1 in artificial sea water increased with increasing fluid velocity. The results of both cycle polarization and EIS measurement showed that the critical flow velocity of film breakdown for BFe30-1-1 in seawater was about 3 m/s. In the low-frequency region of EIS, the linear part disappeared and the inductive loop appeared when flow velocity increased from 2 m/s to 3 m/s, indicating the breakdown of the surface film. All of the tests corresponded with each other.