Microbially influenced corrosion (MIC) is a potentially critical degradation mechanism for a wide range of materials exposed to environments that contain relevant microorganisms. The likelihood and rate of MIC are affected by microbiological, chemical, and metallurgical factors; hence, the understanding of the mechanisms involved, verification of the presence of MIC, and the development of mitigation methods require a multidisciplinary approach. Much of the recent focus in MIC research has been on the microbiological and chemical aspects, with less attention given to metallurgical attributes. Here, we address this knowledge gap by providing a critical synthesis of the literature on the metallurgical aspects of MIC of carbon steel, a material frequently associated with MIC failures and widely used in construction and infrastructure globally. The article begins by introducing the process of MIC, then progresses to explore the complexities of various metallurgical factors relevant to MIC in carbon steel. These factors include chemical composition, grain size, grain boundaries, microstructural phases, inclusions, and welds, highlighting their potential influence on MIC processes. This review systematically presents key discoveries, trends, and the limitations of prior research, offering some novel insights into the impact of metallurgical factors on MIC, particularly for the benefit of those already familiar with other aspects of MIC. The article concludes with recommendations for documenting metallurgical data in MIC research. An appreciation of relevant metallurgical attributes is essential for a critical assessment of a material’s vulnerability to MIC to advance research practices and to broaden the collective knowledge in this rapidly evolving area of study.

Microbially influenced corrosion (MIC) poses a significant threat to metal structures across various industrial sectors, leading to substantial economic losses and potential environmental damages. As deep sea exploration and infrastructure development expand, understanding MIC under high hydrostatic pressure becomes increasingly critical. Microorganisms in these extreme environments must undergo specific structural and metabolic adaptations to survive and thrive. In this study, we employed a proteomic approach to investigate the physiological states and corrosive potential of two sulfate-reducing bacteria (SRB) with different hydrostatic pressure optima. By simulating depths ranging from the sea surface to 3,000 m, we identified species-specific corrosion mechanisms and distinct proteomic profiles associated with pressure adaptation. These findings reveal opposing trends in corrosion rates, emphasizing the complex relationship between microbial physiology and environmental conditions. This study underscores the importance of characterizing microbial responses to hydrostatic pressure for improving corrosion risk assessments and predictive models, particularly for metallic structures deployed in extreme environments. IMPORTANCE: Microbially influenced corrosion (MIC) is a widely studied phenomenon that continues to be poorly understood due to its inherent multifaceted nature. MIC involves complex interactions between microbial communities, their metabolic activities, and the surrounding environmental and material conditions. With the recent rapid expansion of human exploration into previously inaccessible areas, such as the deep sea, new questions about how the physiological adaptations of microbial communities influence their corrosive capabilities have been raised. This study investigates the relationship between corrosion in sulfate-reducing bacteria and the proteomic responses to environmental stresses in differently adapted organisms. It suggests that microorganisms sharing the same core metabolic pathways can drive corrosion through different mechanisms and highlights how hydrostatic pressure adaptations can impact MIC severity.

The formation of biofilms on metal surfaces contributes to the degradation of the metallic materials through a process known as microbially influenced corrosion (MIC). While MIC accounts for a substantial portion of the global corrosion-related costs, its study results particularly challenging when related to infrastructure deployed in extreme environments inhabited by microorganisms, such as the deep sea. Here, this limitation was addressed with a novel high-pressure bio-electrochemostat able to simulate the conditions of the deep sea more accurately than the traditional closed-batch setups. With this device, the corrosive capabilities of the piezophilic sulfate-reducing bacterium (SRB) Pseudodesulfovibrio profundus were analysed at atmospheric pressure and 30 MPa under flow and static conditions. The results highlighted the device's ability to closely replicate environmental conditions, thereby keeping bacterial communities metabolically active throughout the experiments and allowing for a more accurate assessment of the impact of MIC. Furthermore, the comparison between atmospheric and high hydrostatic pressures clearly showed that MIC represents a threat for metallic structures at the bottom of the ocean as much as at surface level.