Electrochemical and Thermodynamic Investigation on Corrosion Inhibition of C38 Steel in 1M Hydrochloric Acid Using the Hydro-Alcoholic Extract of Used Coffee Grounds

Table 4

Electrical parameters and inhibitory effectiveness of C38 steel corrosion in 1 M HCl solution containing different concentrations of the extract.

T	C	R 1	Q 1	n 1	R 2	Q 3	n 3	R 3	R ct	IE
(K)	(g/L)	(Ω cm^2)	(e^−3F cm^−2)		(Ω cm^2)	(e^−3F cm^−2)		(Ω cm^2)	(Ω cm^2)
293.15	Blank	3.626	0.31	0.816	51.54	/	/	/	51.54	—
	0.25	3.42	0.09	0.76	556.3	/	/	/	556.3	90.73
	0.5	4.081	0.08	0.76	906.5	/	/	/	906.5	94.31
	1	1.748	0.06	0.69	1180	/	/	/	1180	95.63
	1.5	3.341	0.03	0.69	1475	/	/	/	1 475	96.50
	2	1.004	0.02	0.64	3272	/	/	/	3 272	98.42
303.15	Blank	3.31	0.36	0.83	36.83	/	/	/	24.9
	0.25	2.03	0.13	0.78	207	/	/	/	207	87.97
	0.5	2.37	0.12	0.78	246	/	/	/	246	89.87
	1	3.612	0.12	0.78	281.8	/	/	/	281.8	91.16
	1.5	2.375	0.12	0.78	322.2	/	/	/	322.2	92.27
	2	2.733	0.05	0.63	1222	/	/	/	1 222	97.96
313.15	Blank	2.82	0.56	0.81	16.29	/	/	/	16.29
	0.25	2.35	0.14	0.78	135	/	/	/	135	87.93
	0.5	2.541	0.14	0.78	158.6	/	/	/	158.6	89.72
	1	2.24	0.12	0.77	177	/	/	/	177	90.79
	1.5	2.22	0.12	0.8	207.3	/	/	/	207.3	92.14
	2	3.266	0.06	0.71	46.41	0.02	0.5	590.8	637.21	97.44
323.15	Blank	3.01	0.61	0.8	10.9	/	/	/	10.9
	0.25	2.248	0.16	0.80	86.95	/	/	/	86.95	87.46
	0.5	2.06	0.16	0.77	103.4	/	/	/	103.4	89.45
	1	2.37	0.16	0.78	107	/	/	/	107.2	89.83
	1.5	2.19	0.13	0.79	134.4	/	/	/	134.4	91.88
	2	3.89	0.02	0.79	133.2	0.007	0.8	282.7	415.9	97.37