Electrochemical and quantum mechanical investigation of various small molecule organic compounds as corrosion inhibitors in mild steel

Mary Stephanie S Carranza,Yves Ira A Reyes,Erick Christofer Gonzales,Danielle P Arcon,Francisco C Franco

doi:10.1016/j.heliyon.2021.e07952

Abstract

The corrosion inhibition property of selected small organic compounds was investigated using electrochemical measurements, including potentiodynamic polarization (PDP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and density functional theory (DFT) calculations. The inhibition efficiency (IE %) of the inhibitor on mild steel (MS) in 1 M HCl was then determined. Results show that the presence of the inhibitors resulted in decreased corrosion current density (Icorr) values and increased polarization resistance (Rp). Furthermore, the use of higher concentrations of inhibitors led to an increased inhibition efficiency. Tafel slopes and shifts in the Ecorr values suggested that the inhibitors tested are mixed-type inhibitors that form a protective layer on the surface of the substrate. Of the organic compound inhibitors tested, the inhibitor 4-ethylpyridine (EP) exhibited the highest Rp values and inhibition efficiency values from the PDP, LPR, and EIS analyses, respectively. DFT calculations showed negative adsorption energies and confirmed the chemisorption of the inhibitors allowing for the formation of a hydrophobic protective film against corrosion and correlations between the quantum chemical values and electrochemical data were demonstrated. The results show the influence of the presence of electronegative O, S, and N atoms, as well as the role of aromatic rings in the promotion of surface protection by preventing aggressive ionic species from binding onto MS.

Highlights

Corrosion of mild steel (MS) is a contending issue in the field of industrial cleaning, mining, chemical processing, petrochemical engineering, material refining, and more
This was followed by 10 mM PY (539.2 Ω cm2, 74.4 % IE) and 10 mM EI (538.7 Ω cm2, 74.3 % IE)
The calculations were performed with the spin-polarized generalized gradient approximation density functional theory (DFT-GGA) of Perdew-Burke-Ernzerhof (PBE) using the plane-wave pseudo-potential method with ultra-soft pseudopotentials (USPP) [47,48]

Summary

Introduction

Corrosion of mild steel (MS) is a contending issue in the field of industrial cleaning, mining, chemical processing, petrochemical engineering, material refining, and more. External corrosion is one of the leading causes of pipeline transportation failure of natural gases, chemicals, and oil, which can lead to damage amounting to US $2.5 trillion in value, which is 3.4% of the global GDP (2013) [1]. Pipeline damage is caused by the corrosive effects of the environment such as soil acidity, oxygen concentrations in the atmosphere/water, CO2 concentrations in brine solutions, environmental temperature, natural catalysts present (i.e., less active metals such as copper or lead), and salt concentrations [2]. The presence of salt can lead to corrosion through the increase in acidity when dissolved in water [3, 4] These factors occur naturally and exist homogeneously in nature, these parameters are accelerants in the corrosion of mild steel

Methods

Results

Conclusion