The inhibiting effect of 1,2,3-benzotriazole (BTAH) against the corrosion of Cu-Ni (90/10) alloy in seawater and seawater polluted with inorganic sulphide was studied by electrochemical impedance studies (EISs), potentiodynamic polarization studies, and cyclic voltammetric (CV) and weight-loss studies. Surface examination studies were carried out by X-ray photo electron spectroscopy (XPS) and scanning electron microscopy (SEM)/energy dispersive X-ray analysis (EDX). EIS studies have been carried out in seawater and 10？ppm of inorganic sulphide containing seawater in the absence and presence of BTAH at different concentrations, different immersion periods, and at different temperatures. Appropriate equivalent circuit model was used to calculate the impedance parameters. The potentiodynamic polarization studies inferred that BTAH functions as a mixed inhibitor. The impedance, polarization, and weight-loss studies showed that the inhibition efficiency of BTAH is in the range between 99.97 and 99.30% under different conditions. Cyclic voltammeric studies show the stability of the protective BTAH film even at anodic potentials of +550？mV versus Ag/AgCl. All these studies infer that BTAH functions as an excellent inhibitor for Cu-Ni (90/10) alloy in seawater and sulphide-polluted seawater. XPS and SEM-EDX studies confirm the presence of protective BTAH film on the alloy surface. 1. Introduction Copper-nickel alloys are extensively used in marine applications because of their good electrical and thermal conductivities, corrosion resistance, and ease of fabrication of the equipment [1]. The 90/10 copper-nickel alloy is a material of selection for condensers and heat exchangers, where seawater is used as a coolant and in desalination plants [2, 3]. This alloy is resistant to stress corrosion cracking by ammonia and sulphide ions [4] and has good resistance to biofouling due to the release of copper ions [5, 6]. This alloy is also resistant to pitting and crevice corrosion in quiet seawater [7]. The corrosion resistance of this alloy is related to the performance of the passive film, which is mainly composed of Cu2O [8–11], though other copper (II) based compounds such as atacamite and cupric oxide are also present in the film [6] after long exposure. The cupric species generally overlies the cuprous species. However, in the sulphide containing seawater, the corrosion rate of Cu-Ni (90/10) alloy is increased as the sulphide ions interfere with the film formation and produce a nonprotective black layer containing cuprous oxide and sulphide ions. The pollution of
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