Effect of organic anions on corrosion studied by mass loss, profilometry, SEM electrochemical methods

摘要

It is demonstrated that organic compounds, and their ions, have varied and sometimes dramatic effects on both the rates and nature of corrosion. Microbial activity has a dominating effect on the composition of organic compounds (i.e. on the metabolic profile); however, their effect on corrosion manifests itself whether microbial growth, including that of biofilm, is present or not. The effects have been studied both in laboratory and industrial settings in the oil- and gas-industry. In controlled laboratory experiments, 1018 carbon steel coupons were exposed to known solutions of selected organic compounds at varying concentrations under aerobic conditions. Compounds/anions studied include, but are not limited to, acetate, lactate, and pyruvate. Corrosion was measured and/or monitored using mass loss measurements, profilometry, electrochemistry and surface analytical methods, such as scanning electron microscopy and XRD. Solutions of pyruvate in oxygenated HPLC water are shown to be extremely corrosive across concentrations and time frames relevant to biocorrosion. In particular, low mM concentrations of pyruvate results in severe pitting corrosion. Experiments demonstrating that such conditions can be produced by microbial metabolism within biofilms, resulting in the formation of deep pits will be presented. The effects of structurally related anions, such as acetate, lactate, and propionate were both varied and dramatically different from that of pyruvate.