Mitigation effects of ammonium on microbiologically influenced corrosion of 90/10 copper-nickel alloy caused by Pseudomonas aeruginosa

Currently, the microbiologically influenced corrosion (MIC) of 90/10 copper-nickel (Cu-Ni) has garnered increased attention. Pseudomonas aeruginosa, a prevalent nitrate-reducing bacteria in seawater, is a notable participant in the process of marine nitrogen cycle. This study seeks to investigate the impact of NH4+ on the corrosion process of 90/10 Cu-Ni alloy in the P. aeruginosa media. The results revealed that the average pit depth of the alloy coupons was 4.4 +/- 0.2 mu m in the P. aeruginosa media, whereas the average pit depth reduced to 2.8 +/- 0.1 mu m in the P. aeruginosa + NH4+ media. In the P. aeruginosa media, the corrosion current density (icorr) was 4.96 x 10-7 A cm -2, while in the P. aeruginosa + NH4+ media, the icorr decreased to 2.45 x 10-7 A cm -2. The excess NH4+ led to a reduction in the P. aeruginosa biofilm thickness (23.4 mu m vs. 35.6 mu m), facilitated the underlying P. aeruginosa sessile cells to obtain energy from free organic carbon more easily. Additionally, the interaction of Cu with NH3 led to the formation of the unstable complex Cu(NH3)2 +, ultimately resulting in the formation of a protective Cu2O layer on the alloy surface, thus mitigating the 90/10 Cu-Ni alloy MIC.