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Various pollutants are often introduced in seawater by wet and dry deposition and by improper dumping of municipal wastewater. These pollutants often affect the corrosivity of seawater on copper-based alloys which might be thought to be resistant in this environment and do not receive sufficient research efforts. In the present investigation the effect was determined of some common pollutants such as urea, sodium sulfite, sodium nitrate, sodium phosphate, copper sulfate, lead acetate, ammonium sulfate, and ammonium chloride at a level of i0 ppm and of chlorine at 1 ppm concentration on the corrosion characteristics of the 90Cu-10Ni and the 70Cu-30Ni alloys in seawater, both in the presence and in the absence of i0 ppm sulfide. Both small amplitude cyclic voltammetry (SACV) and the Tafel extrapolation technique were employed as test procedures. All pollutants under investigation have led to an increase in corrosion rate and their effect was more pronounced when sulfide was also present. The effects of pollutants were more intense on 90Cu-10Ni as compared to 70Cu-30Ni alloys. In unpolluted seawater, the worst pollutant for 90Cu-10Ni alloy is sulfide followed by urea and chlorine, while for the 70Cn-30Ni alloy, the worst pollutant was ammonium chloride followed by sulfide and sodium phosphate. In unpolluted seawater, the introduction of pollutants led to a corrosion reaction which was under cathodic control except for sulfide where the reaction was under anodic control and resulted in a sharp negative shift in the corrosion potential. In sulfide polluted seawater, the worst pollutant for 90Cu-10Ni alloy was ammonium sulfate followed by urea while for 70Cu-30Ni alloy, the worst pollutant was urea followed by ammonium chloride, ammonium sulfate, and sulfite ions.

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Five copper-nickel alloys with nickel contents ranging from 0 weight percent (w/o) to I00 w/o were electrochemically investigated in sulfide polluted seawater (0 to I00 ppm S=). In addition a chromium modified copper-nickel alloy (CDA 722) was also investigated. The purpose of this research is to investigate the effect of both the nickel content and the sulfide ion concentration under a simulated impingement condition. It is found that CDA 722 performs as well as CDA 715 and better than CDA 706 under impingement conditions in both polluted and unpolluted seawater. In addition, three different complexing agents were investigated. It is found that fuchsin or EDTA can have a beneficial effect in reducing the corrosion rate and a combination of two complexing agents can result in a deleterious effect which can explain the premature failures of copper-nickel alloys often reported in the literature.Nickel alloys and particularly copper nickel alloys are commonly used in seawater applications. A great deal of research has concentrated on studying the performance of these alloys in this environment (e.g.,. The corrosion performance of these alloys has been shown to be very suitable in marine service. Although these alloys have been shown to be highly suitable in unpolluted seawater, enhanced corrosion in this environment has been shown to be associated with sulfide contamination. 3-25 These alloys were also shown to be susceptible to impingement attack even in unpolluted seawater. 1' 3' 8' 9' 11 As indicated by Evans, 3 even with the best materials (e.g., pure nickel) there is still the risk of corrosion to condenser tubes if the water used contains hydrogen sulfide or cystine 26 S 9 CH2 -CH(NH2) -COOH

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