Electrochemical Behavior of Copper-Based Materials Exposed to Natural Seawater

摘要

Four surface layers were identified on unpolarized copper-containing materialsexposed in following natural seawater; substratum metal; an inorganic chloride corrosion product layer that contained alloying elements; a biofilm and crystalline, spherical phosphate-rice deposits. All copper surfaces were colonized by bacteria within three weeks of exposure independent of alloy composition. Biofilms on 7OCu:3ONi were thin and formed within the corrosion product layer, whereas the biofilm on all other copper surfaces formed on top of corrosion layers. The complexity of impedance spectra for unpolarized copper-containing materials was attributed to the formation of surface layers and the contributions of charge transfer and mass transport controlled reactions mediated by the layers. Cathodically polarized copper alloys were uniformly covered with calcareous deposits within two weeks of polarizations. Impedance spectra were similar for all polarized alloys after calcareous deposits covered the surfaces. Bacteria colonized the polarized surfaces and the calcareous deposits. Experimental results are compared to electrochemical data previously reported for stainless steels and titanium. Biofouling, Corrosion, Biodeterioration, Electrochemistry.