Corrosion behavior of 70/30 cupronickel in electrolytic seawater antifouling environment

Available chlorine is most commonly used in seawater cooling systems to eliminate biofouling. The corrosion behavior of 70/30 cupronickel alloy after exposure to seawater with different concentrations of available chlorine was studied by electrochemical and immersion tests. The electrochemical measurements show that 100 ppm available chlorine accelerates the corrosion of 70/30 cupronickel alloy in seawater. The corrosion rate of 70/30 cupronickel sample in seawater with 100 ppm available chlorine is 3-4 times higher than that in seawater with 0-10 ppm available chlorine. Scanning Kelvin probe (SKP) and scanning vibrating electrode technique (SVET) results demonstrate that the local electrochemical reaction of 70/30 cupronickel alloy is more active after soaking in seawater with 100 ppm available chlorine. Energy dispersive spectroscopy (EDS) results reveal that Cl element in the corrosion products is enriched after exposure to seawater with 100 ppm available chlorine. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the corrosion product of 70/30 cupronickel sample contains more Cu-2(OH)(3)Cl after being immersed in seawater with 100 ppm available chlorine.