Crevice corrosion of CuNi 90/10 under simulated macrofouling in temperate and tropical Australian marine environments

Copper-nickel 90/10 alloys are widely used in marine environments due to their resistance to corrosion and biofouling. However, the influence of macrofouling on localised corrosion remains poorly understood. This study examines the effect of simulated macrofouling-induced crevices on CuNi 90/10 corrosion using laser-cut plastic shims to replicate hard fouling geometries. Samples with crevice gaps of 50, 130 and 1,000 µm were exposed for 180 days at two Australian marine sites: temperate (Melbourne) and tropical (Cairns). Crevice corrosion was most severe in Melbourne, with the 130 µm gap showing the deepest attack. In Cairns, samples showed lower crevice corrosion despite heavier external fouling, suggesting that fouling composition and protective calcareous deposits may mitigate attack. Crevice interiors lacked Desulfobacterota and exhibited less diverse communities with greater inter-replicate variability at both sites than outside surfaces. These results highlight the combined influence of environment, crevice geometry, corrosion product films, and biofouling composition on crevice corrosion of CuNi 90/10.