Synthesis of new binary trimethoxyphenylfuran pyrimidinones as proficient and sustainable corrosion inhibitors for carbon steel in acidic medium: experimental, surface morphology analysis, and theoretical studies

Abstract

In this study, synthesis and assessment of the corrosion inhibition of four new binary heterocyclic pyrimidinones on CS in 1.0 M hydrochloric acid solutions at various temperatures (30-50 °C) were investigated. The synthesized molecules were designed and synthesized through Suzuki coupling reaction, the products were identified as 5-((5-(3,4,5-trimethoxyphenyl)furan-2-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione (HM-1221), 2-thioxo-5-((5-(3,4,5-trimethoxyphenyl)furan-2-yl)methylene)dihydropyrimidine-4,6(1H,5H)-dione (HM-1222), 1,3-diethyl-2-thioxo-5-((5-(3,4,5-trimethoxyphenyl)furan-2-yl)methylene)dihydropyrimidine-4,6(1H,5H)-dione (HM-1223) and 1,3-dimethyl-5-((5-(3,4,5-trimethoxyphenyl)furan-2-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione (HM-1224). The experiments include weight loss measurements (WL), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). From the measurements, it can be shown that the inhibition efficiency (η) of these organic derivatives increases with increasing the doses of inhibitors. The highest η recorded from EIS technique were 89.3%, 90.0%, 92.9% and 89.7% at a concentration of 11 × 10^-6 M and 298 K for HM-1221, HM-1222, HM-1223, and HM-1224, respectively. The adsorption of the considered derivatives fit to the Langmuir adsorption isotherm. Since the ΔG^o_ads values were found to be between - 20.1 and - 26.1 kJ mol^-1, the analyzed isotherm plots demonstrated that the adsorption process for these derivatives on CS surface is a mixed-type inhibitors. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscope (AFM) and Fourier- transform infrared spectroscopy (FTIR) were utilized to study the surface morphology, whereby, quantum chemical analysis can support the mechanism of inhibition. DFT data and experimental findings were found in consistent agreement.

Keywords: Carbon steel; Corrosion inhibition; Pyrimidinone derivatives; Quantum chemical calculations.

Fig. 1

Synthesis of the new trimethoxyphenylfurylidene-pyrimidinones 5a-d

Fig. 2

WL-time curve for CS in 1.0 M HCl with as well as without different concentrations of inhibitors a-d at 303 K

Fig. 3

Arrhenius plots for CS corrosion in the 1.0 M HCl without as well as after using various concentrations of a–d

Fig. 4

Kinetic transition state plots for CS dissolution in 1.0 M HCl without as well as after utilizing various doses of inhibitors a–d

Fig. 5

The plots of Langmuir isotherm for CS in 1.0 M HCl with altered doses of inhibitors a-d at diverse temperatures

Fig. 6

Various adsorption isotherms of the tested inhibitors for the corrosion of CS in 1.0 M HCl at 303 K

Fig. 7

Vant's Hoff plots (Log K_ads vs. 1000/T) for the adsorption of organic molecules a–d at 303 K on CS surface in 1.0 M HCl

Fig. 8

Changes in E_OCP vs. time for CS in the 1.0 M HCl either alone or with various dosages of organic hybrids a–d at 298 K

Fig. 9

PDP curves for the CS corrosion in 1.0 M HCl at 298 K without and after adding diverse concentrations of inhibitors a–d

Fig. 10

A simple circuit used to suit the EIS results

Fig. 11

Nyquist plot for CS in 1.0 M HCl and with several doses of the inhibitors a-d at 298 K

Fig. 12

Bode plot for corrosion of CS in 1.0 M HCl and in the existence of various doses of organic constitutions a-d at 298 K

Fig. 13

SEM images for CS smooth surface (a), then after 24 h immersion in 1.0 M HCl (b) and in the existence of 11 × 10⁻⁶ M of inhibitors (c-f)

Fig. 14

EDX spectra of CS (a) after 24 h immersion in 1.0 M HCl (b) and in the existence of 11 × 10⁻⁶ M of inhibitors (b–e)

Fig. 15

a Represent smoother image CS surface taken by AFM, whereas, image b indicates what happened after immersion in HCl only, while, images from (c to f) refer to the presence of 11 × 10⁻⁶ M of inhibitors

Fig. 16

FT-IR spectra of a HM-1223, b HM-1222, c HM-1224, and d HM-1221

Fig. 17

HOMO and LUMO electron density maps for the studied inhibitors

Fig. 18

The most suitable adsorption configuration of four inhibitors on Fe (1 1 0) using adsorption locator module

Fig. 19

Mechanism of inhibition of compound (HM-1223, 5c)