Corrosion Inhibition of Mild Steel in Acidic Media by 5′-Phenyl-2′,4′-dihydrospiro[indole-3,3′-pyrazol]-2(1H)-one

Table 3

Activation energies (𝐸_a) and free energy of adsorption (Δ𝐺^∘) for the corrosion of mild steel in 1 M HCl and 1 M H₂SO₄.

			−Δ𝐺^∘ at various temperatures (kJ mol^−1)
Name of the inhibitor	𝐸a (kJ mol^−1)		1 M HCl					0.5 M H2SO4
	HCl	H2SO4	303 K	313 K	323 K	333 K	343 K	303 K	313 K	323 K	333 K	343 K
Blank	26.07	58.97	—	—	—	—	—	—	—	—	—	—
SPAH	48.84	76.02	6.32	6.09	6.05	6.12	5.52	7.80	7.64	7.43	6.27	5.45