The accelerated corrosion of CuNi alloys in sulphide-polluted seawater: Mechanism no. 2

Abstract The corrosion behaviour of copper-nickel alloys in unpolluted and sulphide-polluted seawater has been investigated. It was demonstrated that the co-presence of sulphide and oxygen in seawater results in corrosion rates much higher than those measured when the alloy is exposed alternately to sulphide and oxygen. These high corrosion rates are comparable to the rates reported for the accelerated attack of these alloys in actual polluted estuary environments. This corrosion behavior could be modeled by considering the effect of oxygen and sulphide on the corrosion product. In aerated sulphide-polluted seawater accelerated corrosion appears to be the result of the sulphide preventing the formation of a protective oxide corrosion product layer. In the absence of a passive corrosion product, the anodic process proceeds unabated, supported by the cathodic reduction of oxygen, and extremely high corrosion rates result.