Study on Corrosion Behavior of B30 Cu-Ni Alloy in Simulated Marine Environments

In this article, the influence of CO₃²⁻/HCO₃⁻ on the corrosion behavior of B30 Cu-Ni alloy in 3.5 wt.% NaCl solution was systematically studied utilizing a series of tests. The results demonstrate that the surface film is the primary factor causing different corrosion resistance of B30 alloy in various solutions. The average corrosion rate of B30 alloy immersed in the solution of 3.5% NaCl + 0.05 M NaHCO₃ is 0.123 mm/a, while the alloy in 3.5% NaCl solution containing 0.05 M Na₂CO₃ exhibits the lowest corrosion rate of 0.027 mm/a. The addition of CO₃²⁻ induces a transition from surface activation state to the passivation state, resulting in the formation of a passive film on the alloy surface. Furthermore, B30 alloy exhibits obvious activated characteristic in NaCl solution containing HCO₃⁻, which is attributed to the fact that H⁺ ionized by HCO₃⁻ seriously damages the stable structure of passive film, causing the generation of a corrosion product film with lower protective ability. This indicates that the inhibiting effect of H⁺ on passivation is greater than the promoting impact of CO₃²⁻. Moreover, the substrate of B30 alloy primarily experiences selected dissolution of Cu element.