Combined Effect Of Chloride And pH On Corrosion Resistance Of Cu-10Ni Alloy

Cu-10Ni alloy is a standard heat exchanger material for saltwater (including seawater) applications owing to its excellent thermal conductivity and corrosion resistance. The excellent corrosion resistance is due to formation of Cu2O film, which accords protection. However, when varying amount of H+, OH- and Cl- ions are present, CuCl2- may also form. The CuCl2 is not protective as Cu2O and hence corrosion resistance may be affected. Present paper investigates combined effect of chloride ion and pH on corrosion resistance of Cu-10Ni alloy. Cathodic and anodic polarization test results are presented for saltwater containing various amounts of NaCl at pH 6 and 8. It is found that, i(corr) increases with increasing chloride concentration. The results are discussed using dissolution mechanisms, semi-conducting behaviour of Cu2O film and deterioration of the film in presence of chloride ions.