Corrosion of Metals and Alloys in Conventional and Alternative Fuels: From Biodiesel and Hydrotreated Vegetable Oil to Sustainable Aviation Fuel and e-Fuels—A Critical Review

The transition from petroleum-derived fuels to renewable and synthetic alternatives is changing the chemical environments encountered by fuelstorage, distribution, and engine materials. Biodiesel (fatty acid methyl ester, FAME), hydrotreated vegetable oil (HVO/HEFA), sustainable aviation fuel (SAF), and electro-fuels (e-fuels) differ in polarity, oxygen content, hygroscopicity, oxidative stability, and potential contaminants, resulting in different corrosion risks for metallic materials. This review critically examines recent advances, predominantly from 2020 to 2026, in the corrosion behavior of carbon steel, stainless steel, copper and its alloys, aluminum, and zinc-coated materials exposed to conventional and alternative fuels. The discussion covers water-driven electrochemical corrosion, oxidative–acidic degradation, and microbiologically influenced corrosion (MIC), together with the effects of water content, total acid number (TAN), temperature, storage conditions, blend composition, and fuel contaminants. Available evidence identifies FAME biodiesel as the most extensively studied fuel in terms of corrosion, with copper and copper alloys showing high susceptibility, while stainless steel and aluminum exhibit greater resistance. HVO/HEFA is expected to have a lower corrosion propensity than FAME biodiesel because of its different chemical composition, although direct comparative data remain limited. For SAF and especially e-fuels, direct fuel-phase corrosion data are still scarce, and proposed corrosion tendencies require experimental confirmation. Corrosion assessment methods, including gravimetric immersion testing, standardized fuel tests, electrochemical techniques, and surface characterization, are evaluated together with mitigation strategies based on material selection, antioxidants and corrosion inhibitors, protective coatings, and fuel quality control. The low electrical conductivity of many fuel matrices complicates conventional electrochemical measurements and requires adapted testing approaches. Major research gaps include fuel-phase corrosion characterization of e-fuels, validation of testing protocols for HVO and SAF, sequential exposure to changing fuel chemistries, and the development of predictive corrosion management frameworks. This review links fuel chemistry, corrosion mechanisms, and material compatibility to support material selection and corrosion management in low-carbon fuel systems.