Abstract
Corrosion of 70/30 Cu-Ni alloy by marine aerobic bacteria Pseudomonas sp. NCIMB 2021 in an artificial seawater medium was investigated by electrochemical and microscopic methods. Polarization curve measurements demonstrated that the corrosion rate of the alloy increased notably in the presence of the Pseudomonas sp. by the acceleration of both the anodic and cathodic reactions. The impedance spectra and the corresponding equivalent circuits confirmed that the alloy surface in the sterile medium comprised of an outer organic compound conditioning layer and an inner compact and protective oxide film layer; while in the Pseudomonas inoculated medium, a duplex layer of an outer porous, heterogeneous and non-protective biofilm layer and an inner porous oxide film layer was present. Both the charge transfer resistance, Rct, and the resistance of the porous oxide film, Rpo, decreased with exposure time, indicating an acceleration of corrosion due to the marine bacteria. Bacteria attached to the alloy surface formed blotchy biofilms, as observed by fluorescent microscopy. The dynamic development of the biofilm and surface roughness were monitored by atomic force microscopy. Scanning electron microscopy images showed micro- pitting corrosion on the alloy surface after the biofilm remova
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