Effect of Ni content in CuNi alloys on the repassivation behavior of passive films by Pseudomonas aeruginosa and Desulfovibrio vulgaris

A study employed surface morphology observation, corrosion product composition analysis, and electrochemical measurements to investigate differences in passive film breakdown and repassivation processes between pre-passivated B10 and B30 CuNi alloys under synergistic corrosion by Pseudomonas aeruginosa (P. aeruginosa) and Desulfovibrio vulgaris (D. vulgaris) in seawater, attributable to their differing Ni content. The results show that the growth-metabolic activity of P. aeruginosa and D. vulgaris accelerated the selective dissolution of surface nickel on the alloy. Higher Ni content in the alloys corresponded to increased proportions of Cu₂O and NiO in the pre-formed passive film, resulting in a denser passive layer that provided superior short-term protective properties, manifested by higher total electrochemical impedance and slower pitting corrosion rates. However, these dense film limited the migration of Ni²⁺, resulting in the obstruction of the repair of NiO in the middle and late stages, the poor protection of the passive film and the faster pitting rate. This study indicates that in the seawater environment where P. aeruginosa and D. vulgaris coexist, the pre-passivated CuNi alloy with low Ni content has stronger passive film repair ability and better corrosion resistance in the middle and late stages of immersion.