Adsorption Properties and Inhibition of C38 Steel Corrosion in Hydrochloric Solution by Some Indole Derivates: Temperature Effect, Activation Energies, and Thermodynamics of Adsorption

Table 4

Values of the elements of equivalent circuit required for fitting the EIS for C38 steel immersed in the presence and absence of norharmane at different temperatures.

	Temp (°C)	𝑅ct (Ω cm^2)	𝐴10^4 (Ω^−1 s^𝑛 cm^−2)	𝑛	𝐶dl (𝜇F cm^−2)	𝐿 (H cm^−2)	𝑅𝐿 (Ω cm^2)	IE (%)	𝜃
	25	49 ± 0.02	9.5 ± 0.73	0.853 ± 0.014	546	—	—	—	—
Blank	35	17 ± 0.64	20.5 ± 4.21	0.795 ± 0.421	863	18 ± 1.87	6 ± 1.26	—	—
	45	12 ± 0.94	43.5 ± 3.56	0.745 ± 0.362	1583	15 ± 2.35	3 ± 0.87	—	—
	55	3 ± 0.96	72.8 ± 5.64	0.735 ± 0.093	1834	10 ± 8.54	2 ± 1.25	—	—
0.2 mM	25	148 ± 0.91	2.91 ± 0.02	0.871 ± 0.008	183	—	—	67	0.6689
	35	53 ± 0.43	4.37 ± 0.25	0.836 ± 0.053	209	—	—	60	0.6038
	45	30 ± 0.35	10.88 ± 3.65	0.765 ± 0.059	380	25 ± 4.61	9 ± 1.78	50	0.5000
	55	10 ± 0.65	13.35 ± 1.75	0.815 ± 0.120	501	2 ± 0.40	2 ± 1.37	50	0.5000
0.4 mM	25	238 ± 1.65	1.89 ± 0.19	0.872 ± 0.005	120	—	—	79	0.7941
	35	95 ± 0.89	3.53 ± 0.14	0.829 ± 0.052	175	—	—	78	0.7789
	45	55 ± 3.04	6.19 ± 0.94	0.790 ± 0.032	252	10 ± 1.20	15 ± 1.60	73	0.7273
	55	14 ± 0.93	8.84 ± 2.31	0.831 ± 0.054	362	3 ± 0.21	2 ± 0.32	64	0.6429
0.8 mM	25	514 ± 1.18	0.84 ± 0.03	0.883 ± 0.012	55	—	—	90	0.9047
	35	180 ± 1.04	3.18 ± 0.13	0.825 ± 0.045	173	—	—	82	0.8235
	45	85 ± 1.56	5.01 ± 0.30	0.814 ± 0.023	244	7 ± 0.27	14 ± 0.90	79	0.7857
	55	22 ± 1.55	7.13 ± 0.47	0.809 ± 0.251	267	6 ± 1.60	2 ± 1.10	77	0.7727
1.2 mM	25	641 ± 1.73	0.66 ± 0.02	0.887 ± 0.010	44	—	—	92	0.9236
	35	245 ± 0.55	2.3 ± 0.78	0.803 ± 0.072	114	—	—	91	0.9143
	45	123 ± 0.81	2.9 ± 0.57	0.802 ± 0.140	127	—	—	88	0.8780
	55	25 ± 0.41	4.46 ± 0.17	0.804 ± 0.023	149	6 ± 0.50	3 ± 1.43	80	0.8000