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

Table 4

Some thermodynamic parameters Δ𝑆^∘ and Δ𝐻^∘ for the corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄.

Name of the inhibitor	Δ𝑆^∘ (J/mol/K)		−Δ𝐻^∘ (kJ/mol)
	1 M HCl	0.5 M H2SO4	1 M HCl	0.5 M H2SO4
SPAH	15.7	46.17	60.7	26.52