Inhibition Effects of Amines and Thiols on Iron Corrosion in Anhydrous Methanol Solution Containing FeCl3

Abstract

Polarization and impedance measurements were carried out on an iron electrode in an anhydrous methanol solution of and containing organic corrosion inhibitors. They were alkylamines, N,N‐dimethylalkylamines, and alkanethiols with various carbon numbers. These inhibitors suppressed both cathodic and anodic processes of iron corrosion in the methanol solution by their chemisorption on the surface via sharing electrons between nitrogen or sulfur and iron atoms. X‐ray photoelectron and Fourier transfer infrared reflection spectra of the iron surface treated with the methanol solution containing the inhibitors revealed their adsorption on the surface. The double‐layer capacitances obtained from impedance data for the electrode inhibited with N,N‐dimethylalkylamines and alkanethiols were lower at various potentials near the corrosion potential than the values for the uninhibited electrode, whereas the capacitance values for the electrode inhibited with alkylamines were higher than those for the uninhibited one. It was proposed that the alkylamine molecule is adsorbed on the surface jointly with adsorbed by the formation of a hydrogen bond between and a H‐N group of alkylamine.