Which corrosion mechanism involves microbial activity and can be mitigated by periodic cleaning and biocides?

• A. Stress corrosion
• B. Pitting corrosion
• C. Crevice corrosion
• D. Microbiologic corrosion

Answer: (D)

Microbiologically influenced corrosion involves microbial activity shaping the corrosion process. Microbes form biofilms on metal surfaces, creating localized chemical conditions—such as acidic microenvironments or sulfide production—that accelerate metal dissolution. Periodic cleaning disrupts and removes these biofilms, while biocides reduce the microbial population, slowing or stopping the microbial-driven corrosion. This is different from stress corrosion cracking, which requires both tensile stress and a corrosive environment to propagate cracks; pitting corrosion is a localized chemical attack without necessarily involvement of microbes; crevice corrosion happens in confined spaces with stagnant solution and altered chemistry. The key here is that microbes drive the attack and cleaning plus biocides directly target that microbial aspect to mitigate it.