Corrosion and hydrogen permeation behavior of a marine high-strength steel under the influence of macrofouling organisms

• Macrofouling shifts corrosion from uniform attack to severe localized pitting. • Macrofouling enhances sulfate-reducing bacteria and iron sulfide formation. • Acidification and bacterial metabolites synergistically enhance hydrogen permeation. • Coupled pitting and hydrogen uptake increase environment sensitive cracking risk. Marine biofouling poses a significant threat to the integrity of marine high-strength steel. This study systematically investigated the influence of macrofouling organisms (barnacles, oysters, and mussels) on the corrosion and hydrogen permeation behavior of a marine high-strength steel through real-sea exposure tests and electrochemical analysis. The results revealed that macrofouling transformed the corrosion mode from uniform corrosion to severe localized pitting and crevice corrosion. The formation of occluded cells beneath the attached organisms induced local acidification and chloride enrichment. Furthermore, the proliferation of sulfate-reducing bacteria (SRB) in these microenvironments generated electrically conductive FeS and promoted cathodic depolarization. Crucially, the coupling of acidic occluded cells and SRB metabolic products—which inhibit hydrogen recombination—significantly enhanced the hydrogen permeation flux. This synergistic intensification of localized corrosion and hydrogen uptake markedly increases the material’s susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement. These findings provide essential theoretical insights for the service safety assessment of high-strength steels in marine environments.