Exploring deep insights into the interaction mechanism of a quinazoline derivative with mild steel in HCl: electrochemical, DFT, and molecular dynamic simulation studies

Figures & data

Scheme 1. Synthesis of 3-cyclopropyl-3,4-dihydroquinazolin-2(1H)-one (CPHQ) (4)

Figure 1. Polarization curves of carbon steel in the aggressive solution in the absence and presence of different concentrations of CPHQ at 303 K.

Table 1. PDP parameters of carbon steel in 1.0 M HCl solution without and with different concentrations of CPHQ inhibitor and the corresponding inhibition efficiency at 303 K.

Inhibitor	Concentration (M)	−Ecorr (mV/SCE)	−βc (mV/dec)	βa (mV/dec)	icorr (µA/cm^2)	${\eta }_{PDP}$(%)
Blank	1.0	496	162	132	564	–
CPHQ	5 × 10^-3	463	141	66	22	95
	1 × 10^-3	487	141	85	40	92
	5 × 10^-4	484	144	77	60	89
	1 × 10^-4	477	145	89	69	87

Figure 2. Nyquist plots recorded for carbon steel in 1.0 M HCl solutions without and with different concentrations of the inhibitor CPHQ at 303 K.

Figure 3. Bode impedance plots and phase angle plots recorded for carbon steel without and with various concentrations of CPHQ at 303 K.

Figure 4. Equivalent electrical circuit used to fit the EIS data.

Table 2. Impedance parameters for the corrosion of carbon steel in 1.0 M HCl solution containing CPHQ at 303 K.

Inhibitor	Concentration (M)	Rp (Ω×cm^2)	n	Q × 10^−4 (s^n /Ω × cm^2)	Cdl (μF/cm^2)	${\eta }_{EIS}$ (%)
Blank	1.0	29.35	0.89	1.761	91	–
CPHQ	5 × 10^-3	491	0.81	0.2985	11	94
	1 × 10^-3	418	0.82	0.3058	11	92
	5 × 10^-4	304	0.79	0.4028	12	90
	1 × 10^-4	280	0.80	0.4254	14	89

Table 3. Weight loss data of different concentrations of CPHQ in 1.0 M HCl solution at 303K.

Inhibitor	Concentration (M)	$C_R$ (mg/cm^2 ×h)	${\eta }_{WL}(\%)$	ϴ
Blank	1.0	1.135 ± 0.005	–	–
CPHQ	5x10^-3	0.034 ± 0.008	97	0.97
	1x10^-3	0.079 ± 0.009	93	0.93
	5x10^-4	0.136 ± 0.011	88	0.88
	1x10^-4	0.181 ± 0.008	84	0.84

Figure 5. The variation of the inhibition efficiency derived from electrochemical and weight loss methods as a function of the concentration of the inhibitor.

Table 4. The adsorption parameters for the corrosion of carbon steel in 1.0 M HCl with CPHQ at 303 K.

Inhibitor	Slope	Kads (M^-1)	R^2	$\Delta G_{\text{ads}}^{°}$ (kJ/mol)
CPHQ	1.03	34238	0.9999	−36.4

Figure 6. Plots of the Langmuir adsorption isotherm of the CPHQ on the carbon steel surface at 303 K.

Figure 7. Potentiodynamic polarization curves of carbon steel in (a) 1.0 M HCl and in (b) 1.0 M HCl + 5 × 10⁻³ M of CPHQ at different temperatures.

Table 5. Effect of temperature on electrochemical parameters of the corrosion of CS in 1.0 M HCl in the absence and presence of 5 × 10⁻³ M of CPHQ.

Inhibitor	Temperature (K)	−Ecorr (mV/SCE)	icorr (μA cm^-2)	η (%)
Blank	303	496	564	–
	313	498	773	–
	323	492	1244	–
	333	497	1650	–
CPHQ	303	466	23	95
	313	491	62	91
	323	514	140	88
	333	536	321	80

Figure 8. (a) Arrhenius and (b) transition state plots for carbon steel in 1.0 M HCl and 1.0 M HCl + 5 × 10⁻³ M of CPHQ at different temperatures.

Table 6. Corrosion kinetic parameters for carbon steel in 1.0 M HCl in the presence and absence of 5 × 10⁻³ M of CPHQ.

Inhibitor	Ea (kJ/mol)	ΔHa (kJ/mol)	ΔSa (J mol^-1 K^-1)	Ea − ΔHa
Blank	31.00	28.36	−98.8	2.64
5 × 10^-3 M of CPHQ	72.37	69.73	11.65	2.64

Figure 9. SEM images of CS surface in absence and presence of tested inhibitor at 5 × 10⁻³ concentration after 6 h of immersion time at 303 K.

Figure 10. The optimized molecular structure and frontier orbitals distribution (HOMO and LUMO) of CPHQ molecule calculated at B3LYP/6-31G (d, p).

Table 7. The quantum chemical parameters of CPHQ calculated using DFT at B3LYP/6-31G (d, p).

Inhibitor	EHOMO (eV)	ELUMO (eV)	ΔEgap (eV)	ΔN
CPHQ	−5.5475	−1.4803	4.0672	0.3211

Figure 11. The optimized molecular structure with (a) Mulliken charge and (b) MEP of CPHQ calculated at B3LYP/6-31G (d, p).

Figure 12. Stable configurations for the adsorption of CPHQ on Fe(110) surface obtained from MD simulations.

Table 8. Interaction and binding energies obtained from MD simulations for adsorption of CPHQ on the iron surface.

System	Einteraction (KJ/mol)	Ebinding (KJ/mol)
Fe (110) + CPHQ / 491H2O, 9Cl^− and 9H3O^+	−874.45	874.45