Let’s talk about bacterial corrosion

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Bacterial corrosion occurs when metal corrodes in soil containing sulfates; the hydrogen from the cathodic reaction reduces the sulfates to sulfides, and sulfate-reducing bacteria use the energy from this reaction to reproduce, thereby accelerating the corrosion of the metal. In some oxygen-poor soils that contain sulfates, sulfate-reducing bacteria multiply. During their metabolic processes, they require hydrogen or certain reducing agents to convert sulfates into sulfides, using the energy from this reaction to grow. SO42- + 8H2 → S2- + 4H2O. Due to the presence of sulfates and other H+, the cathodic reaction in the corrosion process of metals in soil results in the generation of atomic hydrogen. In the soil, it adheres to metal surfaces; if it cannot escape as bubbles continuously, cathodic polarization occurs, which significantly slows down the corrosion process. However, the presence of bacteria in sulfuric acid provides a way for atomic hydrogen to be utilized; it reduces SO42- to S2-, which then reacts with Fe2+ to form black FeS deposits. Bacterial reproduction is most favorable when the soil pH is between 5 and 9 and the temperature is between 25 and 30°C.