Inhibition of mild steel and N-80 steel corrosion in presence of dithiazolidine derivatives in 15% boiling hydrochloric acid

Four heterocyclic compounds namely, 3-phenyl imino-5-anisidyl imino-1,2,4-dithiazolidine (PAID), 3-phenyl imino-5-olyl imino- 1,2,4-dithitizolidine (PTID), 3-phenyl imino-5-chloro imino-1,2,4- dithiazolidine (PCID) and 3,5-diphenyl imino-1,2,4-dithiazolidine (DPID) have been synthesized and evaluated as corrosion inhibitors for mild steel (MS) and oil well steel (N-80) in 15% hydrochloric acid (HCl) at temperature 378 2 K by weight loss method. All the heterocyclic compounds showed excellent performance. 3,5-diphenyl imino-1,2,4-dithiazolidine (DPID) has been found to be the best corrosion inhibitor. It exhibited 99.6% inhibition efficiency (IE) for US and 98.4% for N-80 steel at 3000 ppm of inhibitor concentration. The potentiodynamic polarization studies carried out at room temperature on MS and N-80 in 15% HCl containing 500 ppm of the dithiazolidines showed that all the investigated compounds are mixed type inhibitors.