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Microbial activity can represent a significant factor in the degradation of metallic materials. Nevertheless, microbially influenced corrosion of magnesium alloys has received limited attention. This study examines the effect of chlorides, cysteine, and HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) in a methanogen culture medium on corrosion behaviour of the AZ31 alloy (MgAl3Zn1). Electrochemical results show the highest corrosion rate in the complete medium (158.5 µA/cm2). Removing HEPES caused the largest decrease (15.8 µA/cm2), followed by removal of cysteine (50.1 µA/cm2), indicating that both strongly accelerate corrosion. Chloride removal had a smaller effect (125.9 µA/cm2), suggesting that corrosion is not governed by chlorides alone. Corrosion potentials showed only minor changes, indicating kinetic control. Surface analysis revealed severe pitting in the complete medium, while cysteine- and HEPES-free conditions produced smoother surfaces. Fourier-transform infrared spectroscopy (FTIR) confirmed identical corrosion products (Mg(OH)2, carbonates, phosphates) in all cases. Overall, corrosion of AZ31 is driven by the combined action of medium components, with HEPES and cysteine playing a more significant role than chlorides.
Keywords: AZ31 alloy, culture medium, corrosion, methanogens, HEPES, cysteine© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.