Critical Research on Enhancement of the Inhibitor Efficiency of 4-Phenyl-1,2-dithiol-3-thione on Corrosion of Mild Steel for 20% Sulphuric Acid

Substituted 4-phenyl-1,2-dithiol-3-thione (PDTT) synthesized and tested as inhibitors for the corrosion
for mild steel in the presence of oxygen by potentiodynamic polarization and electrochemical
impedance spectroscopy (EIS) technique in 20% H2SO4 at 25ºC. This organic compound inhibits the
acidic corrosion even at low concentration. The results obtained show that this sulfur compound is
good inhibitors and are in good agreement. Polarization curves indicate that 4-phenyl-1,2-dithiol-3-
thione is a cathodic inhibitor and able to reduce the corrosion current, obtained from electrochemical
impedance spectroscopy measurement, were analyzed to model the corrosion inhibition process
through appropriate equivalent circuit model. The adsorption of 4-phenyl-1,2-dithiol-3-thione on the
steel surface in 20% H2SO4 solution, obeys to Langmuir's isotherm with a very high negative value of
the free energy of adsorption Gºad.