Corrosion Behavior of High-Strength C71500 Copper-Nickel Alloy in Simulated Seawater with High Concentration of Sulfide

The corrosion behavior of high-strength {"type":"entrez-nucleotide","attrs":{"text":"C71500","term_id":"2442025"}}C71500 copper-nickel alloy in high concentrations of sulfide-polluted seawater was studied by potentiodynamic polarization measurements, electrochemical impedance spectroscopy (EIS), immersion testing, and combined with SEM, EDS, XPS, and XRD surface analysis methods. The results showed that the {"type":"entrez-nucleotide","attrs":{"text":"C71500","term_id":"2442025"}}C71500 alloy shows activation polarization during the entire corrosion process, the corrosion rate is much higher (0.15 mm/a) at the initial stage of immersion, and the appearance of diffusion limitation by corrosion product formation was in line with the appearance of a Warburg element in the EIS fitting after 24 h of immersion. As the corrosion process progressed, the formed dark-brown corrosion product film had a certain protective effect preventing the alloy from corrosion, and the corrosion rate gradually decreased. After 168 h of immersion, the corrosion rate stabilized at about 0.09 mm/a. The alloy was uniformly corroded, and the corrosion products were mainly composed of Cu₂S, CuS, Cu₂(OH)₃Cl, Mn₂O₃, Mn₂O, MnS₂, FeO(OH), etc. The content of Cu₂S gradually increased with the extension of immersion time. The addition of S²⁻ caused a large amount of dissolution of Fe and Ni, and prevented the simultaneous formation of a more protective Cu₂O film, which promoted the corrosion process to some extent.