Corrosion Inhibitive Effect of Novel Eco Friendly Corrosion Inhibitors for Mild Steel in 0.5 M HCl-A Comparative Study

摘要

Two new Mannich bases: 1-[(4-methylpiperazin-1-yl)(phenyl)methyl]thiourea and 1-[(4-ethylpiperazin-1-yl)(phenyl)methyl]thiourea were synthesised by a cost effective green method. The synthesised Mannich Bases were characterised and tested as corrosion inhibitors for the corrosion of a mild steel surface in 0.5 M hydrochloric acid solution using potentiodynamic polarization and electrochemical impedance spectroscopy. The data obtained from these two methods were in good agreement with each other. The effects of an increase in temperature and a change in the concentration of the inhibitors were studied. The results showed that the inhibition efficiency of both inhibitors increased with an increase in their concentrations. Polarization measurements showed that both compounds acted as mixed type inhibitors. Temperature studies revealed that inhibition efficiency of both compounds increased up to 50 degrees C and beyond which inhibitor efficiency decreased. Both inhibitors showed the maximum inhibition efficiency at 50 degrees C in 500 ppm concentration. The adsorption of inhibitors on a mild steel surface is an endothermic process and is best described by the Langmuir adsorption isotherm. Both kinetic and thermodynamics adsorption parameters were calculated and discussed. The surface adsorbed film was analysed using scanning electron microscopy.