Aqueous Extract of Kalmegh (Andrographis paniculata) Leaves as Green Inhibitor for Mild Steel in Hydrochloric Acid Solution

Table 2

The values of activation parameters 𝐸_𝑎, Δ𝐻^∗_𝑎, and Δ𝑆^∗_𝑎 for mild steel in 1 M HCl in the absence and presence of optimum concentrations of Kalmegh (Andrographis paniculata) extract.

Inhibitor conc. (ppm)	𝐸𝑎 (kJmol^−1)	−Δ𝐻^∗𝑎 (kJmol^−1)	Δ𝑆^∗𝑎 (kJmol^−1)	Δ𝑄 (kJmol^−1)
1 M HCl	29	22	−137	—
1200 ppm	65	62	−36	79