Nanoscopic Imaging of Biogenic Feedstock-Induced Corrosion in Model Petroleum Infrastructure

Biofeedstocks derived from living organisms or their byproducts have recently emerged as an environmentally benign complement to petroleum, diversifying energy production in the petroleum industry from sole dependence on crude oil while utilizing mostly existing petroleum infrastructure. However, biofeedstocks also bring challenges as they can cause distinct and potentially more severe corrosion in metal-based petroleum infrastructure than crude oils due to their higher molecular oxygen content and the presence of various organic acids. To effectively manage such corrosion, it is crucial to understand the corrosion mechanism, particularly the onset of local corrosion, as well as its relationship with the metallic microstructure. Here, using pentanoic acid─a typical degradation product and representative corrosion contributor from biofeedstocks─as the corrosive medium, we capture the real-time initiation and progression in corrosion of carbon steel lamella, which is a model petroleum infrastructure, at nanometer resolution. We correlate in situ liquid-phase transmission electron microscopy imaging of the corrosion process with ex situ characterization of grain size, orientation, and elemental distribution. Through this correlative, multimodal characterization, we identify the key microstructural features that significantly influence corrosion behavior: galvanic corrosion initiates corrosion, strain accelerates corrosion, and lattice orientation guides corrosion propagation. Contrary to aqueous corrosion, corrosion in pentanoic acid is not heavily influenced by the grain boundaries, with similar rates observed in coarse- and fine-grain lamellae. Our observations highlight the importance of intrinsic structural features of carbon steel and their impact on corrosion in biofeedstock-based organic acids, providing insights for potential corrosion mitigation.