Catalytic hydrothermal liquefaction is used to convert wet biomass, industrial waste streams and intermediate bio-products into biofuels through high temperature alkaline catalytic solution. Corrodants such as chloride and sulfide anions released, and organic acids produced during the conversion would inevitably complicate the conversion environments and thus challenge the selection of qualified constructional alloys for the main reactor. Our most recent study revealed that the presence of catalyst, inorganic corrodants and organic acid changed formation and dissolution rates of formed oxide layers on certain Fe-based steels. In this technical paper, studies were carried out on the corrosion performance and oxide layer properties of UNS N08825 through static autoclave tests and advanced microscopic characterizations. The influence of catalyst and corrodants was investigated to understand their impact on corrosion modes and extent of nickel-based constructional alloys in different HTL environments.