Corrosion inhibition effect and adsorption of aniline derivatives on QD36 steel surface in acidic solution

Inhibition of QD36 steel corrosion in 0.5 M HCl solution by aniline derivatives was studied using chemical (weight loss), potentiodynamic polarization and electrochemical frequency modulation measurements. The adsorption process of studied aniline derivatives on steel surface obeys the Langmuir adsorption isotherm. The values of activation energy (E*_a), adsorption equilibrium constant (K _ads), free energy of adsorption (ΔG _ads ^° , adsorption enthalpy (ΔH _ads ^° ) and adsorption entropy (ΔS _ads ^° )were calculated and discussed. Potentiodynamic polarization measurements showed that aniline derivatives are mixed-type inhibitors. The results obtained by EFM technique were shown to be in agreement with other chemical and electrochemical techniques. Scaning electron microscope (SEM) was used to study the surface morphology of the QD36 steel in 0.5 M HCl solution in the absence and presence of inhibitors. Further, theoretical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.