Experimental and theoretical studies of the adsorption and corrosion inhibition of 6-phenylpyridazine-3(2H)-thione on Carbon Steel in 2.0 M H3PO4 solution

Abstract

The corrosion inhibition efficiency of 6-phenylpyridazine-3(2H)-thione (PPT) for carbon steel in 2.0 M H?PO? has been studied using weight loss, polarization, electrochemical impedance spectroscopy and SEM techniques. The results show that PPT is a good inhibitor in 2.0 M H?PO?. Effects of temperature and acid concentration on inhibitive performance were investigated. Polarization curves reveal that PPT acts as a mixed-type inhibitor. The electrochemical impedance spectroscopy showed that the charge transfer resistance increases and the double layer capacitance decreases on increasing pyridazine derivative concentration. Activation energy of corrosion and other thermodynamic parameters such as standard free energy, standard enthalpy, and standard entropy of the adsorption process revealed better and well-ordered physical adsorption mechanism in the presence of PPT. Adsorption isotherms in absence or presence of PPT as inhibitor appropriately fit the Langmuir isotherm. Theoretical investigations have established that the interaction of PPT with the metal steel surface is mainly through the sulphur atom and the  system of the aromatic ring. The molecule…metal surface interactions are strongest in the aqueous acidic solution.