Alkali salts of amino acids as alkaline additives for neutralization of acidic corrosion inhibitors

Abstract

Amino alcohols, typically derived from an oil-based value chain, are frequently used as alkaline additives for neutralization of acidic corrosion inhibitors in industrial metal working fluids. The criterions for 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. We present amino acids as functional, nontoxic, non-hazardous, non-volatile, chemically stable and cheap alkaline additives for common acidic corrosion inhibitors. The resulting mixtures have been evaluated for Co, Ni and Cu-leaching and were analyzed by chip-filter assay, potentiodynamic polarization measurements, electrochemical impedance measurements and gravimetry for corrosion protection of iron and steel in aqueous environment at slightly alkaline pH. Of several amino acids tested, Glu and Tau were found to synergistically interact with several acidic corrosion inhibitors of the carboxylic acid and the phosphonic acid type. Glu had a particularly positive impact on the protective properties of phosphonic acids with low hard water compatibility and served as an antiscalant. Tau had also a positive effect on the anticorrosive properties of several acidic corrosion inhibitors and lead to low levels of Co and Ni-leaching. Glu and Tau might thus serve as commercially and ecologically attractive substitutes for current alkaline additives to acidic corrosion inhibitors.

Glucamines as green alternatives to conventional amino alcohols in metalworking fluids

“…We have noticed the same effect of steric hindrance on the leaching properties of alkaline additives with amino acid derivatives in a previous study. [ 26 ] The observed opposite trend for Cu leaching can be explained by the different complex chemistry of Cu(II) versus Co(III) and Ni(II). Co(III) and Ni(II) prefer octahedral coordination of the metal by three bidentate N/O ligands.…”