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

Table 2

Electrochemical parameters calculated from Tafel plots and the corresponding inhibition efficiencies at various temperatures studied of C38 steel in 1 M HCl containing different concentrations of indole derivates.

Norharmane								Harmane
Temp. (°C)	Con. (mM)	𝐸corr versus SCE (mV)	𝐼corr (𝜇A·cm^−2)	𝑏𝑎 (mV·dec^−1)	𝑏𝑐 (mV·dec^−1)	IE (%)	𝜃	𝐸corr versus SCE (mV)	𝐼corr (𝜇A·cm^−2)	𝑏𝑎 (mV·dec^−1)	𝑏𝑐 (mV·dec^−1)	IE (%)	𝜃
	1 M HCl	−460	232	106	89	—	—	—	—	—	—	—	—
	0.2	−467	67	107	125	76	0.7641	−476	65	110	124	77	0.7711
25	0.4	−476	61	116	122	79	0.7852	−489	55	98	107	81	0.8063
	0.8	−494	52	97	118	82	0.8169	−479	34	113	119	88	0.8803
	1.2	−455	28	93	112	90	0.9014	−492	24	87	107	91	0.9155
	1 M HCl	−454	843	111	109	—	—	—	—	—	—	—	—
	0.2	−473	236	112	144	72	0.7200	−465	212	118	133	75	0.7485
35	0.4	−472	195	109	126	77	0.7687	−470	182	116	136	78	0.7841
	0.8	−470	165	102	131	80	0.8043	−456	154	109	128	82	0.8173
	1.2	−479	98	103	135	88	0.8837	−464	101	103	118	88	0.8802
	1 M HCl	−451	1192	120	109	—	—	—	—	—	—	—	—
	0.2	−501	512	130	146	57	0.5705	−496	413	117	134	65	0.6535
45	0.4	−509	472	112	115	60	0.6040	−488	389	112	125	67	0.6737
	0.8	−505	443	135	135	63	0.6284	−487	335	113	126	72	0.7190
	1.2	−485	352	107	140	70	0.7047	−484	245	110	118	79	0.7945
	1 M HCl	−450	1982	131	116	—	—	—	—	—	—	—	—
	0.2	−509	1023	142	150	48	0.4839	−504	983	136	148	50	0.5040
55	0.4	−497	954	114	156	52	0.5187	−496	852	123	140	57	0.5701
	0.8	−566	867	117	127	56	0.5626	−564	715	110	146	64	0.6393
	1.2	−494	651	109	139	67	0.6715	−515	574	107	132	71	0.7104