A study of the gorse aqueous extract as a green corrosion inhibitor for mild steel in HCl aqueous solution

Figures & data

Table 1. Percentage of corrosion inhibition efficiency for some extracts of natural products.

Inhibitor	Optimum concentration	Metal	Medium	Inhibition efficiency (%)	Ref
Orange peel	400 mg L^−1	C-steel	HCl	95.0	( 29)
Mango peel	600 mg L^−1	C-steel	HCl	91.0	( 29)
Passion fruit peel	500 mg L^−1	C-steel	HCl	90.0	( 29)
Cashew peel	800 mg L^−1	C-steel	HCl	80.0	( 29)
Roasted coffee	1000 mg L^−1	C-steel	HCl	94.0	( 31)
Garlic peel	400 mg L^−1	C-steel	HCl	98.0	( 19)
Bauhinia purpurea	500 mg L^1	C-steel	H2SO4	48.5	( 16)
Ilex paraguarensis	1000 mg L^−1	C-steel	HCl	91.0	( 7)
Grape pomace	3% v/v	C-steel	HCl	83.0	( 5)
Azadirachta indica	28.58 mg L^−1	Mild steel	HNO3	73.6	( 30)
Terminalia catappa	0.4 g L^−1	Mild steel	H2SO4	96.0	( 21)
Hibiscus sabdariffa leaves	15 g/100 mL	Mild steel	HCl H2SO4	73.0 87.1	( 22)
Phyllanthus amarus leaves	4 g L^−1	Mild steel	HCl H2SO4	94.1 88.6	( 28)
Carica papaya leaves	2 g L^−1	Mild steel	H2SO4	93.8	( 17)
Potato peel	1000 mg L^−1	Mild steel	HCl	85.0	( 27)

Table 2. Results of gravimetric tests for mild steel by varying the time and concentration of the extract.

Immersion time (h)	Inhibitor (mg L^−1)	Δm (g cm^−2)	Wcorr (g cm^−2 h^−1)	IE (%)
2	Blank	0.0064	0.003202	–
	100	0.0031	0.001537	52.0
	200	0.0025	0.001276	60.1
	400	0.0019	0.000946	70.5
	800	0.0018	0.000880	72.5
24	Blank	0.0453	0.001890	–
	100	0.0156	0.000651	65.6
	200	0.0067	0.000281	85.1
	400	0.0047	0.000198	89.5
	800	0.0037	0.000156	91.7
48	Blank	0.0569	0.001186	-
	100	0.0176	0.000369	68.9
	200	0.0056	0.000117	90.1
	400	0.0043	0.000090	92.4
	800	0.0035	0.000073	93.8

Table 3. Results of gravimetric tests in the presence and absence of 200 mg L⁻¹ of the gorse extract for 2 h varying the time.

Temperature (°C)	Blank		Gorse
	Δm (g cm^−2)	Wcorr (g cm^−2 h^−1)	Δm (g cm^−2)	Wcorr (g cm^−2 h^−1)	IE%
25	0.007756	0.003878	0.003122	0.001561	59.7
35	0.010614	0.005308	0.004270	0.002135	59.8
45	0.015952	0.007976	0.005289	0.002645	66.8
55	0.024900	0.016462	0.007078	0.004707	71.4

Figure 1. Arrhenius plots: (A) ln W_corr × 1/T and (B) ln(W_corr/T) × 1/T for mild steel in 1 mol L⁻¹ HCl in the absence and presence of gorse extract.

Table 4. Apparent activation energy associated with the corrosion process in the absence and presence of the gorse extract.

	Ea (kJ mol^−1)	ΔH* (kJ mol^−1)	ΔS* (J K^−1 mol^−1)	Ea − ΔH*
Blank	38.3	35.7	−172.0	2.6
200 mg L^−1	28.5	25.9	−212.1	2.6

Figure 2. Polarization curves for the mild steel in 1 mol L⁻¹ HCl in the absence and presence of different concentrations of gorse extract.

Table 5. Electrochemical parameters obtained from polarization curves.

Gorse (mg L^−1)	OCP (mV)	Ecorr (mV)	βa (mV dec^−1)	−βc (mV dec^−1)	jcorr (mA cm^−2)	IE%
Blank	−476	−433	82	131	0.926	–
100	−470	−442	70	106	0.216	76.7
200	−480	−441	51	115	0.070	92.4
400	−484	−457	62	128	0.071	92.3
800	−484	−462	68	137	0.073	92.1
1600	−471	−452	61	155	0.048	94.8

Figure 3. Electrochemical impedance diagrams for mild steel in 1 mol L⁻¹ HCl medium in the presence and absence of different concentrations of gorse extract.

Figure 4. Equivalent circuit used to interpret the electrochemical impedance diagrams obtained for mild steel in the absence and presence of the extract.

Table 6. Electrochemical parameters obtained from the electrochemical impedance spectroscopy.

Gorse (mg L^−1)	Rct (Ω cm^2)	N	Y0 (Ω cm^−2)	fmax (Hz)	Cdl (µF cm^−2)	IE%
Blank	14.2	0.894	294	71.6	154	–
100	54.2	0.892	144	35.5	80.3	73.8
200	84.8	0.868	105	35.5	51.3	83.2
400	131	0.873	83.7	28.1	43.4	89.2
800	154	0.866	81.4	28.1	40.1	90.8
1600	419	0.849	83.6	7.94	46.3	96.6

Figure 5. Langmuir (A), Temkin (B), Flory–Huggins (C) and El-Awady (D) isotherms for the adsorption of gorse extract on the mild steel surface in 1 mol L⁻¹ HCl solution.

Table 7. Adsorption parameters obtained with gorse extract as corrosion inhibitor for mild steel in 1 mol L⁻¹ HCl.

Isotherm	r^2	y = ax + b
Langmuir: C/θ vs. C	0.9992	1.0159x + 42.46
Temkin: θ vs. log C	0.9257	0.1767x + 0.4074
Flory–Huggins: log(θ/C) vs. log(1 − θ)	0.9159	1.2616x − 1.4476
El-Awady: log[θ/(1 − θ)] vs. log C	0.9331	0.7664x − 1.0923

Table 8. Weight-loss measurements for mild steel in 1 mol L⁻¹ HCl solution in the absence and presence of 5-caffeoylquinic acid (5-CQA), quercetin and HMWF.

	Immersion time (h)	Inhibitor (mg L^−1)	Δm (g cm^−2)	Wcorr (g cm^−2 h^−1)	IE%
Blank	24	0	0.0427	0.001779	–
5-CQA	24	100	0.0360	0.001500	15.7
Quercetin	24	100	0.0364	0.001517	14.7
HMWF	24	100	0.0036	0.000152	91.5
HMWF	24	200	0.0034	0.000142	92.0

Figure 6. Electrochemical impedance diagrams for mild steel in 1 mol L⁻¹ HCl medium in the absence and presence of 100 mg L⁻¹ of HMWF.

Table 9. Electrochemical parameters obtained from the electrochemical impedance spectroscopy in the presence of 200 mg L⁻¹ of HMWF.

Gorse (mg L^−1)	Rct (Ω cm^2)	n	Y0 (Ω cm^−2)	fmax (Hz)	Cdl (µF m^−2)	IE%
Blank	14.2	0.894	294	71.6	154	–
HMWF	92.6	0.852	114	35.5	51.1	84.7

Figure 7. A – Morphological analysis of the mild steel surface in 1 mol L⁻¹ HCl medium in the absence of the gorse extract. B – Morphological analysis of the mild steel surface in 1 mol L⁻¹ HCl medium in the presence of 400 mg L⁻¹ of the gorse extract.

Table 10. Absorbance values of the sample containing the gorse extract.

Sample containing gorse extract
Abs1	0.473
Abs2	0.470
Abs3	0.472
Average	0.472

da Rocha, J.C.; Gomes, J.A.C.P ;D’Elia, E. Corros. Sci. 2010, 52, 2341–2348. doi: 10.1016/j.corsci.2010.03.033

 Web of Science ®Google Scholar

Souza, E.C.C.A.; Ripper, B.A.; Perrone, D.; D’Elia, E. Mater. Res. 2016, 19, 1276–1285. doi: 10.1590/1980-5373-mr-2015-0740

 Web of Science ®Google Scholar

Pereira, S.S.A.A.; Pegas, M.M.; Fernandez, T.L.; Magalhaes, M.; Schontag, T.G.; Lago, D.C.; Senna, L.F.; D’Elia, E. Corros. Sci. 2012, 65, 360–366. doi: 10.1016/j.corsci.2012.08.038

 Web of Science ®Google Scholar

de Barros, I.B.; Kappel, M.A.A.; dos Santos, P.M.; Veiga Junior, V.F.; D’Elia, E.; Bastos, I.N. Mater. Res. 2016, 19, 187–194. doi: 10.1590/1980-5373-MR-2015-0494

 Web of Science ®Google Scholar

Souza, T.F.; Magalhães, M.; Torres, V.V.; D’Elia, E. Int. J. Electrochem. Sci. 2015, 10, 22–33.

 Web of Science ®Google Scholar

da Rocha, J.C.; Gomes, A.C.P.; D’Elia, E.; Cruz, A.P.G.; Cabral, L.M.C.; Torres, A.G.; Monteiro, M.V.C. Int. J. Electrochem. Sci. 2012, 7, 11941–11956.

 Web of Science ®Google Scholar

Sharma, S.K.; Mudhoo, A.; Jain, G.; Sharma, J. Green Chem. Lett. Rev. 2010, 3, 7–15. doi: 10.1080/17518250903447100

 Web of Science ®Google Scholar

Eddy, N.O.; Ekwumemgbo, P.A.; Mamza, P.A.P. Green Chem. Lett. Rev. 2009, 2, 223–231. doi: 10.1080/17518250903359941

 Web of Science ®Google Scholar

Murthy, Z.V.P.; Vijayaragavan, K. Green Chem. Lett. Rev. 2014, 7, 209–219. doi: 10.1080/17518253.2014.924592

 Web of Science ®Google Scholar

Okafor, P.C.; Ikpi, M.E.; Uwah, I.E.; Ebenso, E.E.; Ekpe, U.J.; Umoren, S.A. Corros. Sci. 2008, 50, 2310–2317. doi: 10.1016/j.corsci.2008.05.009

 Web of Science ®Google Scholar

Okafor, P.C.; Ebenso, E.E. Pigm. Resin Technol. 2007, 36, 134–140. doi: 10.1108/03699420710748992

 Web of Science ®Google Scholar

Ibrahim, T.H.; Chehade, Y.; Zour, M.A. Int. J. Electrochem. Sci. 2011, 6, 6542–6556.

 Web of Science ®Google Scholar