STUDY OF CORROSION INHIBITION OF CARBON STEEL BY DITHIOLETHIONE ORGANIC COMPOUNDS IN A CHLORURED MEDIUM

Two derivatives of dithioles-1,2 thiones-3 and their salts namely (1): 4-phényl-1,2-dithiol-3-thione, (2):4p-tolyl-1,2-dithiol-3-thione, (3): 3-méthylthio-4-phényl-1,2-dithiolylium and (4): 3-méthylthio-4p-tolyl-1,2--dithiolylium were synthesized and their inhibition of corrosion of carbon steel in hcl solution withph = 6.5 was investigated by electrochemical techniques. inhibition efficiency of various concentrationsof these compounds was determined at room temperature. the four compounds showed a bestperformance, giving inhibition efficiency higher than 93%, even at a very low concentration, the inhibitionefficiency of them follows the order (1) < (2) < (3) < (4). experiences show that dithiolethione salts derivatives are better inhibitors than their origin dithiolethiones. with 100 ppm the inhibition efficiency is 93.36% for the first inhibitor and 95.57% for the second. only with 25 ppm the inhibition efficiency is98.67% for the first salt and 99.10% for the second salt. potentiodynamic polarization studies indicatedthat all four compounds acted predominantly as mixed inhibitors, with adsorption from hcl solution oncarbon steel surfaces obeying temkin’s adsorption isotherm. the heteregenous factors, giving variation of adsorption energy with coverage, have been calculated for all inhibitors. the lower is this factor the higheris the inhibition efficiency. these observations are confirmed by computer calculation of molecule dipoles and electronic densities. for each molecule, dipole and electronic densities have high values and increase as their inhibition efficiencies increase. the values of salt inhibitor dipoles are higher comparatively with those of their origin compounds: 3.543 debye and 3.846 debye for inhibitor (1) and (2), their salts have 5.441 debye and 5.825 debye respectively.