Roasted Coffee Extracts as Corrosion Inhibitors for Mild Steel in HCL Solution

Souza, Elaine Cesar do Carmo Assumpção de; Ripper, Beatriz de Andrade; Perrone, Daniel; D'Elia, Eliane

doi:10.1590/1980-5373-MR-2015-0740

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Articles • Mat. Res. 19 (6) • Nov-Dec 2016 • https://doi.org/10.1590/1980-5373-MR-2015-0740 copy

Roasted Coffee Extracts as Corrosion Inhibitors for Mild Steel in HCL Solution

Authorship SCIMAGO INSTITUTIONS RANKINGS

The behavior of roasted coffee extract and its isolated high molecular weight fraction have been investigated as carbon steel corrosion inhibitors in HCl solution by weight loss measurements, potentiodynamic polarization curves, electrochemical impedance and scanning electron microscopy analysis. All results showed that the high molecular weight fraction, rich in melanoidins, present an important role in the inhibitory action of the roasted coffee extract in the acid corrosion of carbon steel.

Keywords
(A) carbon steel; (B) EIS; (B) polarization; (B) SEM; (C) acid corrosion

	[Inhibitor] (mol L^-1)	OCP (mV/SCE)	E_corr (mV/SCE)	j_corr (mA cm^-2)	β_a (mV/dec)	-β_c (mV/dec)	n (%)
Without inhibitor	0	-490	-446	0.313	61	90	--
Roasted coffee extract	50	-498	-483	0.120	108	113	62
	100	-492	-471	0.076	82	102	76
	300	-503	-481	0.075	96	107	76
	1000	-495	-473	0.049	108	87	84
HMWF	30	-499	-476	0.051	86	102	85
	100	-497	-478	0.059	90	101	82
	300	-513	-493	0.051	97	87	85
	1000	-504	-483	0.042	91	87	87

	[Inhibitor] (mg L^-1)	R_ct (Ω cm²)	f_max (Hz)	Cdl (μF cm-2)	n (%)
Without inhibitor	--	21.0	28.1	270	--
Roasted coffee extract	50	221	14.0	51.5	90
	100	197	14.0	57.7	89
	300	279	14.0	40.8	92
	1000	331	11.1	43.3	94
HMWF	30	239	11.1	60.0	91
	100	233	11.1	61.6	91
	300	292	11.1	49.1	93
	1000	348	11.1	41.2	94

Time h	[inhibitor] mg L^-1	Roasted coffee extract		IE (%)	HMWF		IE (%)
		Wcorr			Wcorr
		g cm^-2 h^-1	mm/y		g cm^-2 h^-1	mm/y
6	0	0.002630	29.3	--	0.002630	29.3	--
	50	0.000778	8.67	70	0.000544	6.06	79
	100	0.000586	6.53	78	0.000481	5.36	82
	200	0.000420	4.68	84	0.000455	5.07	83
	300	0.000386	4.30	85	0.000399	4.45	85
	400	0.000361	4.02	86	0.000353	3.93	87
	1000	0.000296	3.30	89	0.000319	3.56	88
24	0	0.002213	24.7	--	0.002213	24.7	--
	50	0.000235	2.62	89	0,000190	2.12	91
	100	0.000198	2.21	91	0.000208	2.32	91
	200	0.000190	2.12	91	0.000172	1.92	92
	300	0.000145	1.62	93	0.000161	1.79	93
	400	0.000113	1.26	95	0.000156	1.74	93
	1000	0.000132	1.47	94	0.000123	1.37	94
48	0	0.001456	16.2	--	0.001456	16.2	--
	50	0.000358	3.99	75	0.000112	1.25	92
	100	0.000100	1.11	93	0.000113	1.26	92
	200	0.000088	0.981	94	0.000097	1.08	93
	300	0.000079	0.880	95	0.000099	1.10	93
	400	0.000079	0.880	95	0.000094	1.05	94
	1000	0.000066	0.736	96	0.000083	0.925	94

	Blank		Roasted coffee extract			HMWF
T (°C)	W_corr		W_corr		n (%)	W_corr		n (%)
T (°C)	(g cm^-2 h^-1)	mm/y	(g cm^-2 h^-1)	mm/y	n (%)	(g cm^-2 h^-1)	mm/y	n (%)
35	0.005031	56,1	0.001261	14.1	75	0.001283	14.3	74
45	0.009137	102	0.001659	18.5	82	0.001711	19.1	81
55	0.013038	145	0.002249	25.1	83	0.002203	24.6	83
65	0.019981	223	0.002831	31.6	86	0.002835	31.6	86

Species	Ea (kJ moL^-1)	Correlation coefficients (r)
Blank	39.0	0.9961
Roasted coffee extract	23.6	0.9992
HMWF	22.8	0.9999

5-CQA	W_corr		IE
mg L^-1	g cm^-2 h^-1	mm/y	%
0	0.001782	19.9	-
100	0.001499	16.7	16
200	0.001300	14.5	27
400	0.001133	12.6	36
Caffeine	W_corr		IE
Caffeine	g cm^-2 h^-1	mpy	%
0	0.001782	19.9	-
100	0.001350	15.0	24
200	0.001220	13.6	32
400	0.001058	11.8	41

Inhibitor	W_corr		IE
mg L^-1	g cm^-2 h^-1	mm/y	%
0	0.001782	19.9	-
100 (5-ACQ) + 100 (caffeine)	0.001289	14.4	28
200 (5-ACQ) + 200 (caffeine)	0.000941	10.5	47

Isotherm	r²		y = a + bx
Adsorption	Coffee Extract	HMWF	Coffee Extract	HMWF
Langmuir: C/θ vs. C	0.9999	0.9999	17.16 + 1.111x	11.39 + 1.128x
Temkin: θ vs. logC	0.9040	0.9620	0.4898+ 0.1411x	0.678+ 0.0683x
Flory-Huggins: log(θ/C) vs. log(1-θ)	0.9514	0.9561	-0.355 + 2.698x	1.551 + 4.977x

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