Equilibrium constant and adsorption free energy of the investigated inhibitors (I & II) adsorbed on C-steel surface at 25 °C.

Langmuir isotherm
Inhibitor	K × 10−5, M−1	, kJ mol−1	Slope	R 2
Inhibitor (I)	5.07 ± 0.015	32.5 ± 0.1454	1.206	0.9720
Inhibitor (II)	6.97 ± 0.025	33.3 ± 0.2189	1.113	0.9910