The Role of Metallurgical Features in the Microbially Influenced Corrosion of Carbon Steel: A Critical Review

Abstract

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.

Keywords: carbon steel; grain size; inclusions; metallurgy; microbially influenced corrosion; microorganisms; microstructure.

Figure 1

Classification of steel types based on chemical composition (with chemical compositions sourced from the ASM Handbook [9]).

Figure 2

Schematic diagram showing grains and grain boundaries at (a) microscopic and (b) atomic levels.

Figure 3

Schematic diagram showing effect of cooling rate on grain size.

Figure 4

Schematic diagram showing effects of deformation and post-deformation heat treatment on grain size.

Figure 5

Iron–carbon phase diagram [96].

Figure 6

Different zones and boundaries in welded metal [176].

Figure 7

Influence of the welding process on the base metal microstructure [176].