High temperature corrosion in various grades of vegetable and waste oils used for bio-fuel production

Corrosion experiments were conducted at 220 °C in vegetable and waste oils used to produce biofuels. Industrial oils and model solutions with controlled concentrations of free fatty acids (FFA) were used. Corrosion of carbon steel and low alloy steel increased with FFA concentration up to several millimeters per year. AISI 316 L stainless steel was immune to corrosion in all FFA concentrations used in this study. Test solution analysis with various techniques allowed identifying corrosion mechanisms involving consumption of FFAs and the formation of highly soluble metal complexes.