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 arti ficial sea water with different fluid velocities has been studied by using a rotating cylinder apparatus. The methods adopted in the experiment were w eight-loss test, linear and cycle polarization, free corrosion potential an d electrochemical impedance spectrum (EIS) measurements as well as SEM obse rvation and EDX analysis. The major emphasis of the study was placed on the critical flow velocity. The results showed that the constant of linear pol arization for the corrosion reaction of BFe30-1-1 in artificial sea water i ncreased with increasing fluid velocity. The results of both cycle polariza tion and EIS measurement showed that the critical flow velocity of film bre akdown for BFe30-1-1 in seawater was about 3 m/s. In the low-frequency regi on 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 t he surface film. All of the tests corresponded with each other.