The Inhibitory Action of the Extracts of Adathoda vasica, Eclipta alba, and Centella asiatica on the Corrosion of Mild Steel in Hydrochloric Acid Medium: A Comparative Study

Table 6

Calculated values of activation energy (𝐸_𝑎), enthalpy of adsorption (Δ𝐻), free energy of adsorption (−Δ𝐺), and entropy of adsorption (Δ𝑆) in the absence and presence of the optimum concentration of the plant extracts.

System	Temp (T) in K	𝐸𝑎 (KJ mol^−1)	Δ𝐻 (KJ mol^−1)	Δ𝐺 (KJ mol^−1)	Δ𝑆 (KJ mol^−1)
Blank	303	31.38	28.86
	313		28.78
	323		28.69
	333		28.61
	343		28.53
	353		28.45
Adathoda vasica 6% v/v	303	62.41	59.89	−17.18	0.2544
	313		59.81	−17.27	0.2463
	323		59.72	−16.71	0.2367
	333		59.64	−16.42	0.2284
	343		59.56	−15.26	0.2181
	353		59.48	−14.82	0.2105
Eclipta alba 8% v/v	303	93.48	90.96	−18.78	0.3622
	313		90.88	−16.31	0.3425
	323		90.79	−15.04	0.3277
	333		90.71	−14.02	0.3145
	343		90.63	−13.22	0.3028
	353		90.55	−11.29	0.2885
Centella asiatica 10% v/v	303	31.33	28.81	−8.75	0.1240
	313		28.73	−9.04	0.1207
	323		28.64	−9.28	0.1174
	333		28.56	−9.68	0.1148
	343		28.48	−9.88	0.1118
	353		28.40	−10.19	0.1093