Glycerol and malonic acid as corrosion inhibitors seen through the density functional theory perspective

Abstract

Glycerol (G) is the major co-product of biodiesel in the transesteri-fication process. As the clean energy demand increases, the G production also increases and new ways of re-using it are needed. In the last decade, some experimental studies claimed that G and its derivative, malonic acid (MA), could be used as corrosion inhibitors. Yet, at the present, there is few evidence of it and more studies are needed to confirm that G and MA would have a good performance in metal protection. The present work aims to study the reactivity of G and MA, since reactivity and inhibition are intimately linked. Density functional theory (DFT) at the B3YLP/6-31G++ level of theory was used to study both molecules? reactivity. The global and local quantum parameters derived are used to assess the reactivity of both molecules. Analysis of the calculated reactivity descriptors suggest that G and MA should exhibit an acceptable corrosion efficiency, but MA showed greater potential as corrosion inhibitor.

Corrosion Resistance of Steel S355MC in Crude Glycerol

“…The corrosion inhibition is probably related to the adsorption of glycerol molecules on the metal's surface. The density functional theory calculations indicated that adsorption happened mainly through oxygen atoms [22]. The protective crude glycerol layer became thicker as the concentration of the inhibitor increased.…”