Effect of organic carbon sources on the anodic corrosion of magnesium AZ31B by sulfate-reducing prokaryote

Abstract

Corrosion caused by sulfate-reducing prokaryotes (SRP) is an important cause of magnesium alloy anode failure in oil pipeline. In this study, the effects of Desulfovibrio sp. HQM3 on the corrosion behavior of AZ31B magnesium alloy anode in organic carbon sources with different contents in simulated tidal flat environment were analyzed using weight loss test, surface analysis and electrochemical analysis technologies. The results showed that the weight loss rate of coupons in low carbon sources contents (0%, 1%, 10%) was higher than that in 100% carbon sources. Electrochemical analyses showed that the corrosion current density (J _corr) under low carbon sources contents was larger, while the charge transfer resistance (R _ct) was lower, leading to a higher corrosion rate compared to those under 100% carbon sources content. Observations from scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) revealed more severe pitting corrosion on the alloy surface in the absence of carbon sources. In addition, a large number of nanowires were observed between bacteria on the alloy surface using SEM. Combined with thermodynamic calculations, it was demonstrated that the corrosion of coupons by Desulfovibrio sp. HQM3 in the absence of carbon sources was achieved through extracellular electron transfer.

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Central South University