This study seeks prevent and alleviate the failure of magnesium alloy anodes in pipelines, which we suspect is a problem related to SRB. The electrochemical corrosion behaviour of two kinds of magnesium alloys, AZ31B and AZ63B, in 3.5 wt.% NaCl solution with sulphide or phosphide—the two main inorganic metabolites of sulphate-reducing bacteria—were studied by electrochemical tests combined with other characterisation methods such as scanning electron microscopy and X-ray diffraction. The results show that the corrosion film formed by inorganic metabolites of SRB’s initial stage of corrosion (1–3 d) can lead to the corrosion of magnesium alloys. However, the loose and porous corrosion product film cannot protect the substrate effectively. The inorganic metabolites in the solution can accelerate the corrosion of the surface of magnesium alloy after the corrosion products have fallen off. This study provides a theoretical basis for alleviating the premature failure of magnesium alloy anodes and for corrosion protection in the future.

At present, there are few studies on microbial corrosion of magnesium anode materials that provide protection for oil pipelines in tidal flat environment. In view of an abnormal failure of magnesium anodes in oil pipelines in a tidal flat mud environment, the influence of the change in water content in the beach mud on the corrosion of AZ31B magnesium anode by sulfate-reducing prokaryote (SRP) was investigated by electrochemical methods, weight loss and surface analysis techniques. SRP can grow well in a tidal flat mud environment and cause microbial corrosion of magnesium alloy. The results show that with the increase in water content, the number of SRP cells in the mud increased, that the corrosivity of tidal flat muds was enhanced and that the corrosion rate of AZ31B magnesium anode was accelerated: compared with the corrosion rate of 0.554 mm/y in 40% water content, the corrosion rate of magnesium alloy samples in 60% water content is as high as 1.38 mm/y.

The effects of organic metabolites produced by a sulfate-reducing prokaryote (SRP) in seawater on the anode corrosion process of magnesium alloy were analyzed by open circuit potential, electrochemical impedance spectroscopy, polarization curve, and other electrochemical methods, combined with scanning electron microscopy and X-ray diffraction. It was found that the product film produced by magnesium alloy anode corrosion was not dense, and the surface of the magnesium anode substrate was exposed during the corrosion process. The corrosion of magnesium anode matrix was accelerated by the simulation of different organic metabolites including mannose, glucuronic acid, and glucose. Thus, the synergistic effect of various metabolites produced by SRP in the corrosion process of magnesium alloy may be considered in future studies.