Sulfate-reducing bacteria (SRB) can regulate environmental pH because of their metabolism. Because local acidification results in pitting corrosion, the potential capacity of pH regulation by SRB would have important consequences for electrochemical aspects of the bio-corrosion process. This study focused on identifying the effect of pH on the corrosion of duplex stainless steel 2205 in a nutrient-rich artificial seawater medium containing SRB species, Desulfovibrio vulgaris. Duplex stainless steel samples were exposed to the medium for 13 days at 37°C at pH ranging from 4.0 to 7.4. The open-circuit potential value, sulfide level, pH and number of bacteria in the medium were recorded daily. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to study the properties of the biofilms at the end of the experiments and the corrosion behaviour of the material. Inductively coupled plasma mass spectrometry was used to measure the concentration of cations Fe, Ni, Mo, Mn, Cr in the experimental solution after 13 days. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX) were used for surface analysis. The results showed the pH changed from acidic values set at the beginning of the experiment to approximately pH 7.5 after 5 days owing to bacterial metabolism. After 13 days, the highest iron concentration was in the solution that was initially at pH 4 accompanied by pitting on the stainless steel. Sulfur was present on all specimens but with more sulfur at pH 4 in the EDX spectra. EIS showed the film resistance of the specimen at pH 4 was much lower than at pH 7.4 which suggests the corrosion resistance of the stainless steel was better at higher pH. The results of this study suggest that the corrosion process for the first few days exposure at low pH was driven by pH in solution rather than by bacteria. The increasing pH during the course of the experiment slowed down the corrosion process of materials originally at low pH. The nature and mechanism of SRB attack on duplex stainless steel at different acidic environments are discussed.

硫酸盐还原菌 (SRB) 通过新陈代谢可以调节环境 pH 值。由于局部酸化会导致点蚀，SRB 调节 pH 值的潜在能力将对生物腐蚀过程的电化学方面产生重要影响。本研究的重点是确定 pH 值对双相不锈钢 2205 在含有 SRB 物种（脱硫弧菌）的营养丰富的人工海水介质中的腐蚀的影响。双相不锈钢样品在 37°C、pH 值范围为 4.0 至 7.4 的条件下暴露于介质中 13 天。每天记录开路电位值、硫化物水平、pH和培养基中的细菌数量。使用电化学阻抗谱（EIS）和动电位极化来研究实验结束时生物膜的特性和材料的腐蚀行为。13天后采用电感耦合等离子体质谱法测定实验溶液中阳离子Fe、Ni、Mo、Mn、Cr的浓度。使用扫描电子显微镜和能量色散 X 射线光谱 (EDX) 进行表面分析。结果显示，由于细菌代谢，5天后pH值从实验开始时设定的酸性值变为约pH 7.5。13 天后，溶液中的铁浓度最高，最初 pH 为 4，同时不锈钢上出现点蚀。所有样品中均存在硫，但在 EDX 光谱中，pH 4 时硫含量更高。EIS 显示样品在 pH 4 时的膜电阻远低于 pH 7.4 时的膜电阻，这表明不锈钢在较高 pH 下的耐腐蚀性能更好。这项研究的结果表明，在低 pH 值下最初几天的腐蚀过程是由溶液中的 pH 值驱动的，而不是由细菌驱动的。实验过程中pH值的增加减缓了原本处于低pH值的材料的腐蚀过程。讨论了不同酸性环境下SRB对双相不锈钢的侵蚀性质和机理。