Corrosion mitigation of carbon steel using triazole Mannich base derivatives: Correlation of electrochemical studies with quantum chemical calculations

Figures & data

Table 1. Various triazole and Mannich base derivatives were found effective against corrosion.

Inhibitor	Metal	Medium	Inhibition efficiency	Reference
3-Methyl-1,2,4-triazole-5-thione	Low carbon steel	1M HCl	90%	AitHaddou et al. (2016)
1,12-Bis(3-méthyl-5(1,12-triazolyl)thiol) dodécane	Low carbon steel	1M HCl	95%
Ethyl 2-(4-phenyl-1H-1,2,3-triazole-1-yl)acetate	Mild steel	1M HCl	97%	Nahlé et al. (2021)
2-(4-Phenyl-1H-1,2,3-triazol-1-yl)acetohydrazide	Mild steel	1M HCl	97%
4-Amino-3-(2-bromo-5-methoxyphenyl)-1H-1,2,4-triazole-5(4H)-thione	Mild steel	1M HCl	95%	Al-Amiery et al. (2020)
N-(1-Morpholinobenzyl) semicarbazide	Aluminium alloy	0.5 M HCl	98%	Maithili et al. (2022)
3-Oxo-3-phenyl-N,N-dimethyl propanamine hydrochloride	Mild steel	0.5M HNO3		Sharma et al. (2014)
3,5-Dioxo-5-phenyl-N,N-dimethyl pentanamine hydrochloride	Mild steel	0.5M HNO3

Scheme 1. Synthesis of Mannich bases 4MPT, PPT and MPT.

Figure 1. Open circuit potential plots of 4MPT, PPT and MPT.

Figure 2. Nyquist plots for the corrosion control of carbon steel in 1 M HCl in the presence and absence of 4MPT, PPT and MPT.

Figure 3. Bode plots for the corrosion control of carbon steel in 1 M HCl in the presence and absence of 4MPT, PPT and MPT.

Figure 4. An equivalent circuit model for EIS results for the studied system.

Table 2. The data obtained from fitted EIS curves for corrosion control of carbon steel with the presence and absence of 4MPT, PPT and MPT.

Inhibitor	Concentration (ppm)	Rs (Ω / cm^2)	Rp (Ω / cm^2)	n	Cdl (μF cm^2)	θ	IE (%)
Blank	0	0.35	12.62	0.91	67.29	–	–
4MPT	50	0.36	91.34	0.89	42.68	0.86	86.18
	100	0.33	113.14	0.90	19.99	0.89	88.84
	250	0.47	131.43	0.89	39.63	0.90	90.40
	500	0.32	147.33	0.90	21.02	0.91	91.43
	750	0.40	175.50	0.89	38.33	0.93	92.81
PPT	50	0.41	69.72	0.88	36.81	0.82	81.90
	100	0.44	83.57	0.89	36.50	0.85	84.90
	250	0.47	111.80	0.88	42.46	0.89	88.71
	500	0.60	132.80	0.89	43.23	0.90	90.50
	750	0.40	189.70	0.90	20.68	0.93	93.35
MPT	50	0.37	103.40	0.90	20.27	0.88	87.79
	100	0.36	109.60	0.89	37.16	0.88	88.49
	250	0.58	122.60	0.89	36.18	0.90	89.71
	500	0.38	134.20	0.89	35.11	0.91	90.60
	750	0.45	170.20	0.89	40.60	0.93	92.59

Figure 5. Potentiodynamic polarization plot for the corrosion control of carbon steel in 1 M HCl by different concentration of inhibitors.

Table 3. Results for the inhibitory effect of 4MPT, PPT and MPT on carbon steel by potentiodynamic polarization and linear polarization resistance experiments.

PDP							LPR
Inhibitor	Concentration (ppm)	Icorr (µA / cm^2)	−Ecorr (mV / Ag/AgCl)	βa (V/dec)	βc (V/dec)	θ	IE (%)	Rp (Ω / cm^2)	θ	IE (%)
Blank	0	1330.0	498	105.7	108.3	–	-	11.7	–	–
4MPT	50	151.0	485	81.9	93.3	0.89	88.65	93.7	0.88	87.51
	100	146.0	490	77.9	103.1	0.89	89.02	118.7	0.90	90.14
	250	103.0	477	74.8	92.3	0.92	92.26	140.9	0.92	91.70
	500	123.0	479	74.3	106.8	0.91	90.75	160.0	0.93	92.69
	750	71.5	463	62.4	94.5	0.95	94.62	184.6	0.94	93.66
PPT	50	232.0	492	98.0	95.9	0.83	82.56	70.8	0.83	83.48
	100	187.0	492	90.1	94.8	0.86	85.94	85.4	0.86	86.30
	250	109.0	473	68.6	94.7	0.92	91.80	112.6	0.90	89.61
	500	109.0	477	80.1	91.8	0.92	91.80	147.2	0.92	92.05
	750	105.0	480	68.8	100.7	0.92	92.11	202.2	0.94	94.21
MPT	50	178.0	498	80.4	100.5	0.87	86.62	109.4	0.89	89.31
	100	122.0	476	69.9	96.9	0.91	90.83	115.8	0.90	89.90
	250	98.0	472	62.9	91.4	0.93	92.63	133.8	0.91	91.26
	500	91.6	480	75.6	82.6	0.93	93.11	143.7	0.92	91.86
	750	66.3	465	64.3	91.4	0.95	95.02	178.8	0.93	93.46

Table 4. Results for the inhibitory effect of 4MPT, PPT and MPT on carbon steel by electrochemical frequency modulation method.

Inhibitor	Concentration (ppm)	βa (mV/dec)	βc (mV/dec)	CR (mpy)	θ	IE (%)	CF (2)(2) $$C_{\mathrm{dl}}\mathrm{ }=\mathrm{ }{[Y_0\mathrm{ }\times \mathrm{ }{\left(R_{\mathrm{p}}\right)}^{1\mathrm{ }\text{-}\mathrm{ }n}]}^{1/n}\mathrm{ }$$(2)	CF (3)(3) $$\theta \mathrm{ }=\frac{R_{\mathrm{p}\left(\mathrm{Inh}\right)}\text{-}\mathrm{ }{R}_{\mathrm{p}\left(\mathrm{Blank}\right)}}{R_{\mathrm{p}\left(\mathrm{Inh}\right)}}$$(3)
Blank	0	35.1	40.4	170.6	–	–	1.572	3.929
4MPT	50	90.1	116.3	25.9	0.85	84.78	1.905	3.186
	100	98.9	113.2	21.3	0.87	87.49	1.909	2.943
	250	85.3	121.3	18.1	0.89	89.39	1.927	2.942
	500	102.4	117.4	18.6	0.89	89.11	1.781	2.729
	750	88.4	101.9	13.0	0.92	92.38	1.557	3.036
PPT	50	90.2	169.0	36.6	0.79	78.53	1.943	2.956
	100	84.7	129.0	27.0	0.84	84.16	1.950	2.990
	250	90.5	110.3	21.3	0.88	87.53	1.868	3.095
	500	88.0	122.6	19.3	0.89	88.67	1.929	2.995
	750	107.5	118.3	15.7	0.91	90.78	1.787	3.007
MPT	50	96.6	114.7	22.4	0.87	86.87	1.870	3.275
	100	87.6	109.3	19.9	0.88	88.30	1.851	2.856
	250	86.2	124.8	19.5	0.89	88.53	1.921	3.037
	500	87.4	124.5	17.9	0.90	89.53	1.889	2.886
	750	161.9	108.4	14.2	0.92	91.71	1.746	2.721

Table 5. Calculated values of K_ads and ΔG^o_ads determined by electrochemical techniques for carbon steel with 4MPT, PPT and MPT.

Inhibitor	Technique	R^2	Kads (M^−1)	ΔG^0ads (kJ mol^−1)
4MPT	EIS	0.99989	48718	−36.70
	PDP	0.99897	42514	−36.36
	LPR	0.99995	57533	−37.11
	EFM	0.99927	37854	−36.07
PPT	EIS	0.9995	23207	−34.86
	PDP	0.99995	44264	−36.46
	LPR	0.99968	25157	−35.06
	EFM	0.99977	26381	−35.18
MPT	EIS	0.99971	46151	−36.57
	PDP	0.9998	43491	−36.42
	LPR	0.99983	57509	−37.11
	EFM	0.99962	45657	−36.54

Figure 6. Scanning electron micrographs (first row) and EDX graphs (second row) of C1018 steel samples: (a) polished fresh metal (b) Immersed in 1 M HCl solution (c–e) Immersed in 1 M HCl solution containing 4MPT, PPT and MPT.

Table 6. The atomic percentage of metal in the presence and absence of 4MPT, PPT and MPT.

Element	Metal	Metal with HCl	Metal with 4MPT	Metal with PPT	Metal with MPT
Si	0.7	–	0.51	0.63	0.87
O	–	11.8	1.59	1.59	1.62
C	–	5.4	3.56	4.12	3.71
S	0.3	0.4	0.38	0.39	0.36
Fe	98.2	82.0	93.95	93.27	93.43

Figure 7. Frontier orbital energetic positions of 4MPT, PPTand MPT molecules.

Table 7. Calculated quantum chemical parameters for 4MPT, PPT and MPT by DFT computation study.

Parameters	4MPT	PPT	MPT
Energy of highest occupied molecular orbital (Ehomo)	−6.4399	−5.8571	−5.9682
Energy of lowest unoccupied molecular orbital (Elumo)	−1.9288	−1.8509	−1.9043
Energy gap (ΔE)	4.5112	4.0062	4.0639
Chemical hardness (η)	2.2556	2.0031	2.0320
Chemical softness (σ)	0.4433	0.4992	0.4921
Ionization potential (I)	6.4399	5.8571	5.9682
Electron affinity (A)	1.9288	1.8509	1.9043
Electronegativity (χ)	4.1844	3.8540	3.9363
Fraction of electron transferred (ΔN)	0.1409	0.2411	0.2175

Figure 8. The Fukui indices density distributions of 4MPT, PPT and MPT.

Figure 9. Electrostatic Potential maps of 4MPT, PPT and MPT.

Figure 10. Top and side views of the most stable low energy configurations for the adsorption of 4MPT, PPT and MPT molecules on Fe (110)/100 H₂O interface obtained using Monte Carlo simulations.

Table 8. The parameters calculated by the Monte Carlo simulation for the most stable adsorption configurations of inhibitor molecules on Fe (110)/100 H₂O system (all units in kcal mol⁻¹).

System	Adsorption energy	Rigid adsorption energy	Deformation energy	Inhibitor: ΔEad/ΔNi	Water: ΔEad/ΔNi
4MPT /Fe (110)/100H2O	−1511.52	−1587.17	75.64	−162.75	−12.28
PPT /Fe (110)/100H2O	−1514.11	−1589.68	75.56	−165.72	−11.72
MPT /Fe (110)/100H2O	−1499.23	−1570.25	71.02	−174.71	−12.29

Figure 11. Possible interaction between the surface of C1018 carbon steel and inhibitor 4MPT, PPT and MPT.

AitHaddou, B., Chebabe, D., Dermaj, A., Benassaoui, H., Assyry, A., Hajjaji, N., … Srhiri, A. (2016). Comparative study of low carbon steel corrosion inhibition in 1M HCl by 1,2,4-triazole-5-thione derivatives. Journal of Materials and Environmental Science, 7, 2000–2191.

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