Glucamines as green alternatives to conventional amino alcohols in metalworking fluids

Abstract

Amino alcohols like triethanolamine (TEA), 2-amino-2-methylpropanol (AMP), or 1-aminopropan-2-ol (MIPA) are common ingredients in industrial metalworking fluids. They are used in large quantities as alkaline additives for the neutralization of acidic corrosion inhibitors and are typical industrial products from the oil-based value chain. The criteria for the selection of these additives have changed in the last decades and are nowadays not only performance-driven but influenced by ecological considerations, toxicity, and regulatory standards. In this study, we evaluate the sugar derivative N,N-diethylglucamine (DEGA) for use as a functional, nonvolatile, chemically stable, and cheap alkaline additive for common acidic corrosion inhibitors. Electrochemical analyses confirm anticorrosive properties of DEGA comparable to the gold standard TEA for iron and steel in an aqueous environment at a slightly alkaline pH. In addition, DEGA leads to extremely low levels of Co, Ni, and Cu leaching and can thus also serve as a nonvolatile substitute for currently used low-leaching additives such as AMP and MIPA. The diethylamino-motif is a sweet spot among different glucamine derivatives tested because it combines easy synthetic accessibility with good water solubility and low-leaching properties. Besides this, DEGA can be prepared in one step from glucose and diethylamine, both derived from renewable resources.