Performance of two new epoxy resins as potential corrosion inhibitors for carbon steel in 1MHCl medium: Combining experimental and computational approaches

The novelty of the work is to investigate the application of two new epoxy resins namely as hexaglycidyl N-phenylaminopropoxy-N.N.N-triphenyl propane-1.3-diamine (ERH) and octaglycidyl N.N.N.N-tetraphenylaminoN.N.N.N-tetrapropoxy methylene dianiline (ERO) as potential corrosion inhibitors for carbon steel (CS) in 1 M HCl medium. The corrosion resistance was quantified by various techniques namely polarization curve (PC), electrochemical measurement (EIS), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), global quantum chemical descriptors (GQCDs) and molecular dynamics (MDs) simulation. EIS data suggest that the corrosion efficiency of ERO (94.1%) is higher than that of the ERH (89.7%) in HCl medium at room temperature. Further, PC results indicate that the corrosion efficiency of ERO (95.6%) is higher than that of the ERH (95.4%) in the presence of 10(-3) M of studied inhibitors and also PC data suggest that the two epoxy resins investigated acted as a mixed type inhibitor. Langmuir adsorption isotherm is the most acceptable technique or method to describe the ERH and ERO epoxy resins adsorption on the CS area. SEM/EDS data display the two ERH and ERO epoxy resins can be stopped the acid attack though chemisorption on the CS surface. GQCDs calculations were applied by density functional theory (B3LYP and WB97XD) and Hartree-Fock (HF) methods using 6-31G(d,p) basis sets to study the inhibition efficiencies of the two epoxy resins inhibitors. GQCDs such as EHOMO, ELUMO, energy gaps, electronegativity, hardness, electrophilicity, fractions of electron transferred were calculated and discussed. Other energetic parameters such the free energy of adsorption, the metal-inhibitor energy gaps, the electron transfer back-donation energy and the initial molecule-metal interaction energy were also calculated and discussed. The molecular dynamics simulation approach was performed to investigate the adsorption behaviors of the investigated inhibitors on Fe(110) surface. The results obtained using the computational methods and the molecular dynamics simulations reveal that the ERO inhibitor has more inhibitory effect against corrosion of the Fe-metal than that of the ERH inhibitor. The obtained theoretical results were adapted with experimental inhibition efficiency results.

Automated summary

The study investigates the application of two new epoxy resins as corrosion inhibitors for carbon steel in a hydrochloric acid medium. Various techniques were utilized to quantify the corrosion resistance and results showed that one of the resins had a higher efficiency compared to the other. Computational methods and molecular dynamics simulations revealed the inhibitory effect of the resins on the metal surface.