The Corrosion of Ni-Cr-Mo Alloys in Aprotic Organic Solvents

Synthesis of chemicals and pharmaceuticals often requires a series of intermediate steps involving reactions in aprotic organic solvents. Many of these solutions can be aggressive towards the metallic materials that constitute the reaction vessels used, so often corrosion-resistant alloys of the Ni-Cr-Mo family are employed. Ni-Cr-Mo alloys are known to exhibit outstanding corrosion resistance in reducing and oxidizing aqueous solutions because of their passive oxide film. However, the application of passive alloys in non-aqueous solvents raises additional concerns due to: i) limited availability of passivating species; ii) different behavior of aggressive halides and acids as a result of the physicochemical properties of the solvent. Due to the scarcity of data on corrosion in organic solvents, the selection of materials for such applications is often based on the literature on aqueous corrosion. The aim of this work is to investigate the corrosion of Ni-Cr-Mo alloys in aprotic organic solvents and to explain the effect of variables such as solvent chemical properties, residual water, alloy chemical composition, and the presence of chlorides and organic oxidants. Ultimately, this work will provide fundamental understanding of the passivity of Ni-based alloys in organic solvents, assisting the selection of materials for non-aqueous applications.