N-substituted methyl ethylenediamine derivatives as corrosion inhibitors for carbon steel in 1 M hydrochloride acid

Abstract

Three N-substituted methyl ethylenediamine derivatives, tetramethylethylenediamine (TDA), pentamethyldiethylenetriamine (PTA), and hexamethyltriethylenetetramine (HTA) were prepared for the corrosion inhibition of 20# steel in 1 M HCl solution. Their corrosion inhibition properties were investigated using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) measurements, and surface analysis techniques. Quantum chemical calculations and molecular dynamics (MD) simulations were applied to analyze the molecular structure-activity relationship of corrosion inhibitors. The results indicated that all three methyl ethylenediamine derivatives exhibited excellent inhibition properties. The order of inhibition efficiency of these inhibitors was TDA < PTA < HTA. Furthermore, all three inhibitors act as mixed-type inhibitors and mainly inhibited the cathodic reaction. The adsorption mechanism of corrosion inhibitors follows the Langmuir isotherm and proceeds by physisorption and chemisorption. The results of quantum chemical calculations and MD simulations effectively support the experimental results. The excellent corrosion inhibition property is attributed to the interaction between tertiary amine groups and Fe, which effectively inhibits corrosion.