Adsorption Behaviour of Pyrazolo [3, 4-b] Pyridine on Corrosion of Stainless Steel in HCl Solutions

Abstract

The properties of stainless steel makes the alloy suitable for many application; but this tends to change at very aggressive conditions thereby making its properties to fail. The corrosion inhibition efficiency of 2-(4-Methyl-3-oxo-2-phenyl-2, 3-dihydro-1H-pyrazolo [3, 4-b] pyridin-4-yl) acetic acid butylester (PP) on stainless steel in HCl solution was studied by weight loss method. The adsorption mechanism was investigated using adsorption isotherms. The experimental data fit Flory-Huggins and Thermodynamic/El-Awady models. The values for free energy of adsorption, ΔGoads, of PP at different surface coverage, θ, were also calculated by applying the mathematical model of Bockris-Swinkels adsorption isotherm. The variation of free energy of adsorption ΔGoads.with surface coverage, θ, was rationalised in term of interaction between adsorbed PP molecules. A possible adsorption model of PP molecules on to the steel surface was suggested.