Corrosion Behavior of Type 304 Stainless Steels in Highly Concentrated Lithium Salt Solutions

Abstract

In this paper, we report that the electrochemical behavior and dissolution of type 304 stainless steel in highly concentrated lithium trifluoromethanesulfonate (LiOTf) solutions depend strongly on the molar fraction of free water molecules in these solutions. Raman spectroscopy of the solutions revealed that the chemical state of the water molecules varied drastically depending on the concentration of the LiOTf solution. More water molecules were found to be coordinated to Li ions in 20 mol% LiOTf solution than that in the 5 mol% solution, resulting in fewer free water molecules in the former. The oxidation of water was suppressed whereas the dissolution of Fe and Cr, which are the main constituents of stainless steel, was enhanced in the 20 mol% LiOTf solution compared to that in 5 mol% solution, except for the dissolution of Fe at higher potentials.

Fig. 6 Schematic of the state of molecules present in the 5 mol% and 20 mol% LiOTf solutions.