Corrosion Inhibition of Mild Steel by S-benzyl-O,O′-dialkyldithiophosphates in HCl Solution

In present work, the target compounds of S-benzyl-O,O'-dialkyldithiophosphates including S-benzyl-O,O'-diphenyldithiophosphate (Inhi-1), S-benzy1-O,O'-dibenzyldithiophosphate (Inhi-2), S-benzyl-O,O'-di(2-phenyl ethyl)dithiophosphate(Inhi-3) and S-benzyl-O, O'-di (4-methylphenyl)dithiophosphate (Inhi-4) were prepared, which acting as corrosion inhibitor for mild steel (MS) in HCl solution were investigated by weight loss measurement, potentiodynamic polarization measurement and electrochemical impedance spectroscopy. The potentiodynamic polarization measurement indicates that the four synthesized compounds are all the mixed-type inhibitor for MS corrosion in HCl solution. Furthermore, all measurements in this study show that the inhibition efficiency increases with inhibitor concentration increasing. Weight loss measurement reveals that inhibition efficiency decreases with HCl concentration and temperature increasing. In addition, the adsorption of Inhi-1, Inhi-2, Inhi-3 and Inhi-4 on MS surface obeys Langmuir isotherm, which are mixed adsorption involving both physisorption and chemisorption.