The inhibition performance of heterocyclic compounds on Q235 steel in methanol/formic acid medium: Experimental and theory

Abstract

The present paper discusses the adsorption and inhibitory effect of nitrogen-containing compound, 1-dodecyl-3-methyimidazolium chloride (DMIC), dodecylpyridinium chloride (DPC) and hexadecylpyridinium chloride monohydrate (HDPC) on Q235 steel corrosion in a new system（10 mol·L−1 methanol/0.1 mol·L−1 formic acid medium. The experimental study was carried out using a series of techniques such as weight loss, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). contact angle test, Raman spectra, X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM) served to identify microscopic variation on Fe surface. Adsorption isotherm model controlling the adsorption process are calculated and discussed. Moreover, the relationships between molecular structure and corrosion inhibition performance of three inhibitors were verified by quantum chemical calculation and molecular dynamics simulation. The results obtained from the electrochemical methods showed that DMIC, DPC and HDPC imparted high resistance and behaved as mixed-type corrosion inhibitors dominated with anode. inhibition efficiency (η%) increased with the increase of inhibitors concentration to attained 88.81%, 92.69%, 93.67% at 0.06 mol·L−1, respectively. Surface studies confirmed the existence of an adsorption film on the metal surface. The obtained results demonstrated that the adsorption process on the metal surface followed the Langmuir adsorption model. Quantum chemical calculations and molecular dynamics simulation (MD) testified the effect of the chemical structure of three inhibitors on its inhibition efficiency, which had a good agreement with the experimental data.