Influence of dithiazolidines on corrosion inhibition for mild steel in sulphuric acid solution

Weight loss measurements and potentiodynamic polarization studies show that 3,5-diphenyl-imino-1, 2,4-dithiazolidine (DPID), 3-phenyl-imino-5-chlorophenyl-imino-1, 2,4-dithiazolidine (PCID), 3-phenyl-imino-5-tolyl-imino-1, 2,4-dithiazolidine (PTID) and 3- phenyl-imino-5-anisidyl-imino-1, 2-4dithiazolidine (PAID) act as effective corrosion inhibitors of mild steel in 1 N H2SO4. PAID performed best, giving inhibition efficiency as high as 99.8% at 500 ppm. All the compounds exhibited more than 90% inhibition efficiency even at concentration as low as 25 ppm. Potentiodynamic polarization studies showed inhibition was under anodic control. Adsorption on the mild steel surface followed by Temkin's adsorption isotherm. The values of activation energy and free energy of adsorption were also calculated.