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

Table 3

Thermodynamic parameters calculated from Tafel plots for the adsorption of indole derivates in 1 M HCl on the C38 steel at different temperatures.

Con. (mM)	Norharmane			Harmane
	𝐸𝑎 (kJ mol^−1)	Δ𝐻𝑎 (kJ mol^−1)	Δ𝑆𝑎 (J mol^−1 K^−1)	𝐸𝑎 (kJ mol^−1)	Δ𝐻𝑎 (kJ mol^−1)	Δ𝑆𝑎 (J mol^−1 K^−1)
HCl	24.42	23.29	−119.48	—	—	—
0.2	31.73	30.60	−99.81	31.20	30.07	−101.88
0.4	32.38	31.25	−98.12	31.80	30.67	−100.43
0.8	33.40	32.27	−95.27	35.18	34.05	−90.53
1.2	37.99	36.85	−81.97	36.89	35.76	−86.63