On the Effects of Common Pollutants on the Corrosion of Copper‐Nickel Alloys in Sulfide Polluted Seawater

Abstract

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.

Optimization of the cathode material for nitrate removal by a paired electrolysis process

“…The pitting potential of Cu decreases from 200 to 55 mV and its corrosion current increases from 4.7 to 10.4 mA cm −2 with ammonia addition. Actually, in the presence of ammonia, the copper oxide layer is destabilized by the formation of the soluble [Cu(NH 3 ) 6 ] 2+ complex [36,37]. For pure nickel and cupro-nickel electrodes, NH 3 with chloride produce various soluble complexes (e.g., NiCl 2 (NH 3 ) 4 , [Ni(H 2 O) 5 NH 3 ] 2+ ) which can lead to a general or localized corrosion [36,37].…”

“…Actually, in the presence of ammonia, the copper oxide layer is destabilized by the formation of the soluble [Cu(NH 3 ) 6 ] 2+ complex [36,37]. For pure nickel and cupro-nickel electrodes, NH 3 with chloride produce various soluble complexes (e.g., NiCl 2 (NH 3 ) 4 , [Ni(H 2 O) 5 NH 3 ] 2+ ) which can lead to a general or localized corrosion [36,37]. However, pure nickel and Ni-Cu alloys remain much more resistant to corrosion than copper with one order of magnitude lower corrosion current density (Table 1).…”

A review of the effects of benzotriazole on the corrosion of copper and copper alloys in clean and polluted environments

“…There is a large number of variables, e.g., composition of the material, concentration of pollutants, environments… etc. In spite of the high corrosion resistance of these alloys, they suffered from severe corrosion in media polluted by sulfide ions [18,20,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84]. This is a problem of considerable significance in view of the fact that many industrial water streams and indeed some natural water bodies are polluted by dissolved sulfides.…”

Corrosion Inhibition of Cu-Ni (90/10) Alloy in Seawater and Sulphide-Polluted Seawater Environments by 1,2,3-Benzotriazole

“…With the increase in immersion time, the shi in is much higher than the shi in . is is due to the depletion of sulphide with the increase in immersion time due to the formation of a thick cuprous sulphide �lm at the surface [41]. According to De Sanchez and Schiffrin [14] and Kato et al [42]; the main effect of copper sulphide is to accelerate the charge transfer of oxygen reduction, thereby controlling the reduction current density by a diffusive transport through the liquid layer adjacent to the electrode, and this is manifested as the increase in .…”