Application of an Aqueous Extract of Cotton Seed as a Corrosion Inhibitor for Mild Steel in HCl Media

Hernandes, Isabel da Silva; Cunha, Jéssica Nogueira da; Santana, Carolina Araujo; Aquino Rodrigues, José Guilherme; D’Elia, Eliane

doi:10.1590/1980-5373-MR-2020-0235

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Articles • Mat. Res. 24 (1) • 2021 • https://doi.org/10.1590/1980-5373-MR-2020-0235 copy

Application of an Aqueous Extract of Cotton Seed as a Corrosion Inhibitor for Mild Steel in HCl Media

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The present work aims to study the aqueous cotton seeds extract as a natural inhibitor of the corrosion of mild steel in 1 mol L⁻¹ HCl using gravimetric tests, potentiodynamic polarization curves, electrochemical impedance measurements and surface morphological analysis by scanning electron microscopy (SEM). The aqueous cotton seed extract acted as a good corrosion inhibitor reaching an inhibition efficiency of 95.7% after 24 h of immersion for 800 mg L⁻¹ inhibitor concentration. For the gravimetric tests varying the temperature, a decrease of the activation energy (Ea) was observed, suggesting a chemical adsorption on the surface of the metal. 400 mg L⁻¹ of the high molecular weight fraction isolated from the total extract showed inhibition efficiency equal to 800 mg L⁻¹ of the total extract, 97.3% and 94.2% from electrochemical impedance and polarization curves data, respectively, suggesting that the macromolecules present a fundamental participation in the inhibitive process.

Keywords:
Mild steel; corrosion inhibitor; cotton seed; natural products

Immersion	[ACSE]	*W_corr*	IE(%)	SD_IE(%)
time (h)	(mg L ⁻ ¹)	(g cm ⁻ ²h ⁻ ¹)	IE(%)	SD_IE(%)
2	0	2.8 x 10⁻³	-	-
	200	6.7 x 10⁻⁴	76.1	0.5
	400	5.4 x 10⁻⁴	80.7	0.5
	800	5.0x 10⁻⁴	82.1	1.5
24	0	1.5 x 10⁻³	-	-
	200	9.0 x 10⁻⁵	94.0	1.3
	400	8.7 x 10⁻⁵	94.2	1.4
	800	6.4 x 10⁻⁵	95.7	1.7

Temperature (°C)		With
	Blank	Inhibitor	IE (%)	SD_IE (%)
	W_corr (g cm⁻²h⁻¹)	W_corr (g cm⁻²h⁻¹)
25	2.8 x 10⁻³	5.0 x 10⁻⁴	82.1	0.7
35	4.5 x 10⁻³	7.0 x 10⁻⁴	84.4	1.6
45	7.0 x 10⁻³	1.0 x 10⁻³	85.7	1.0
55	1.2 x 10⁻²	1.3 x 10⁻³	89.2	0.4

	E_a(kJ mol^-1)	*ΔH (kJ mol^-1)**	*ΔS (J mol^-1 K^-1)**
Blank	39.0	36.4	−172
ACSE	26.2	23.6	−166

[Inhibitor] (mg L⁻¹)	f_max (Hz)	n	Y₀ (µMho sⁿ cm ⁻ ²)	C_dl (µF cm ⁻ ²)	R_p (Ω cm²)	IE (%)
0	71.6	0.895	250	131	16.2	-
10	22.3	0.852	103	49.5	141	88.5
50	17.6	0.827	79.0	35.0	300	94.6
100	8.75	0.821	84.6	41.3	442	96.3
200	8.75	0.829	80.5	40.6	482	96.6
400	6.93	0.824	81.3	41.8	521	96.9
800	5.48	0.824	74.6	40.0	603	97.3
HMWF	6.93	0.836	71.6	38.6	603	97.3

Isoterms		Line Equation	R²
Langmuir	$\frac{C}{θ} = \frac{1}{K} + C$	y= 1.0264x + 1.4645	0.9999
Temkin	$θ = (\frac{- 2.303}{2 a}) log K + (\frac{- 2.303}{2 a}) \log C$	y= 0.0449x + 0.8576	0.7816
Flory-Huggins	$\log (\frac{θ}{C}) = \log K + x \log (1 - θ)$	y= 2.7585x + 1.6563	0.8974
El-Awady	$\log (\frac{θ}{1 - θ}) = \log K + y l o g C$	y= 0.3475x – 0.6174	0.8977

*Inhibitor*	*E_OCP*	*E_corr*	*j_corr*	−*β_c*	*β_a*			IE
*(mg L⁻¹)*	*(mV vs SCE)*	*(mV vs SCE)*	*(mA cm⁻²)*	*(mVdec⁻¹)*	*(mVdec⁻¹)*			*(%)*
0	−503	−447	6.69 x 10⁻¹	121		76.9	–
10	−479	−459	7.90 x 10⁻²	110		78.8	88.2
50	−496	−466	4.09 x 10⁻²	166		72.1	93.9
100	−494	−470	4.12 x 10⁻²	167		67.7	93.8
200	−492	−468	4.06 x 10⁻²	170		73.3	93.9
400	−497	−473	4.05 x 10⁻²	167		80.5	93.9
800	−490	−469	3.88 x 10⁻²	167		86.4	94.2
HMWF	−493	−462	3.91 x 10⁻²	180		75.5	94.2

[Inhibitor]	θ	(1−θ)	Normalized	Normalized
[Inhibitor]			*R_p*	*C_dl*
(mg L ⁻¹ )			(Ω cm²)	(µF cm ⁻ ^²2 He X, Mao J, Ma Q, Tang Y. Corrosion inhibition of perimidine derivatives for mild steel in acidic media: electrochemical and computational studies. J Mol Liq. 2018;269:260-8. )
Aqueous cotton seeds extract
0	-	-	16.2	131
10	0.885	0.115	16.2	430
50	0.946	0.054	16.2	648
100	0.963	0.037	16.4	1116
200	0.966	0.034	16.4	1194
400	0.969	0.031	16.2	1348
800	0.973	0.027	16.3	1481
HMWF
400	0.973	0.027	16.3	1430

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