Thermodynamic and Adsorption Behavior of eco-Friendly Purine Derivatives on the Corrosion of Carbon Steel in 1 M HCl

The behavior of carbon steel in 1.0 mol dm-3 HCl in the presence of novel purine inhibitors namely 1H-pyrazolo[3,4-d]pyrimidin-4(2H)-one (PPO) and 6-[(1-methyl-4-nitro-5-imidazolyl)sulfanyl]purine (ISP) in the concentration range (1×10−4 − 5×10−3 mol dm−3) was studied using weight loss, open circuit potential, potentiodynamic polarization electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. Potentiodynamic polarization shows that PPO and ISP act as mixed-type inhibitors. The values of the activation energy, equilibrium constant, free energy of adsorption, activation enthalpy and activation entropy were discussed. The adsorption of inhibitors on metal followed Langmuir’s adsorption isotherm. The values of suggest the chemical adsorption of PPO and ISP on carbon steel surface.