Thermal selection of microbial consortia modulates copper corrosion toward mineral stabilization

Copper corrosion can be strongly modulated by microbial activity despite the intrinsic toxicity of copper ions to most microorganisms. This study investigates the corrosion behavior of high-purity copper (Cu ≥ 99.9 wt%) exposed to thermophilic bacteria and methanogenic archaea collected from a biological methanation plant. Batch experiments were conducted at 45 °C for 15 days, using the inoculum as-is (biotic), or after three distinct treatments: 1) boiling (120 min), which did not significantly alter the overall-community-level diversity and structure; 2) double autoclaving (121 °C, 20 min), which selectively enriched thermotolerant populations, and 3) sterilization, only achieved by combining autoclaving (121 °C, 60 min), filtration (Φ = 0.22 μm), and UV exposure. Microbial communities were characterized by 16S rRNA gene sequencing; corrosion was monitored by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Raman spectroscopy. Results reveal a time-dependent transition from microbially influenced corrosion (MIC) to microbial corrosion-inhibition (MICI). Bacterial-dominated communities transiently perturbed interfacial electrochemistry and delayed passivation but did not produce the highest cumulative copper dissolution (3,1, 3,73, 3,09 mg L−1, for biotic, boiled, and autoclaved inoculum, respectively). Two distinct MICI pathways were identified: Cu2O barrier stabilization under archaeal-dominated inoculum (autoclaved), and diffusion resistance through porous phosphates precipitation in mixed bacterial-archaeal communities (biotic, boiled inoculum). Sterile conditions exhibited uninhibited chloride-driven localized corrosion and the highest copper release (7.1 mg L−1). Overall, the microbial community exerts a net moderating influence on copper dissolution, and thermal selection of community composition determines which MICI mechanism prevails.