Microbiological Characterization of Natural Seawater Collected on the Brazilian Atlantic Coast—Impact on Carbon Steel Corrosion

ABSTRACT The study investigates microbiologically influenced corrosion (MIC) in metallic materials in seawater, a significant problem for maritime activities and consequently threatens the structural integrity of subsea equipment. Seawater samples from the Brazilian Atlantic coast were analyzed by 16S rRNA amplicon sequencing analysis under two experimental conditions: simulation of long‐term storage (MW01) and microbial corrosion with fresh samples (MW02 and MW03). The experiments showed biofilm formation and differing corrosion behaviors. Microscopic analysis indicated a more intense localized corrosion in MW02, possibly due to the high presence of Halomonas . Analysis revealed significant Bacteria and Archaea diversity, with a predominance of Thermoproteota in MW01 and Pseudomonadota in MW02 and MW03. Sulfate‐reducing bacteria were detected in MW03, although in low percentages. The study highlights the complex interactions between microbial communities and corrosion mechanisms in natural seawater, providing a baseline for future research on mitigation strategies in marine environments.