Effect of Hypochlorite Ions on Corrosion of Cu-Ni Alloys Immersed in Seawater at Turbulent Flow Conditions

A corrosion study of Cu-Ni (90-10) alloy was carried out in natural seawater adding several concentrations of an oxidant biocide (hypochlorite-based biocide). The corrosion tests were made at atmospheric pressure, static and turbulent flow conditions (1000 rpm) and room temperature during 24 hours. A rotating cylinder electrode (RCE) was used in order to get the hydrodynamic conditions. The electrochemical techniques used in the corrosion studies were lineal polarization resistance (Rp), electrochemical impedance spectroscopy (EIS) and polarization curves (PC). A scanning electron microscope (SEM) to carry out the superficial analysis and characterize the corrosion type was used. At turbulent flow condition, the corrosion rate (CR) of the Cu-Ni sample decreased as the concentration of hypochlorite ions increase, while at static condition the CR increased as the hypochlorite ions also increase. A mix corrosion process was observed. Pitting and crevice corrosion was detected, and the mechanism was a differential aeration cell.