STUDY OF CORROSION OF BRASS COATED STEEL CORDS IN THE ACETONITRILE SOLUTION OF SULFENAMIDE DERIVATIVES BY TAFEL PLOT AND AC-IMPEDANCE MEASUREMENTS

Corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives, N-Cyclohexylbenzothiazole-2-sulfenamide (CBTS ), N,N'-Dicyclohexylbenzothiazole-2-sulfenamide (DCBS), N-tert-Butylbe nzothiazole-2-sulfenamide (TBBS), N-tert-Amylbenzothiazole-2-sulfenami de (TABS), and N-Oxydiethylbenzothiazole-2-sulfenamide (OBTS) was inve stigated by potentiostatic anodic and cathodic polarization (Tafel plo t), DC polarization resistance, and AC impedance measurements. The cor rosion current densities and rates are 1.236 muA/cm2 and 0.655 MPY for CBTS; 1.881 muA/cm2 and 0.988 MPY for DCBS; 2.367 muA/cm2 and 1.257 M PY for TBBS; 3.398 muA/cm2 and 1.809 MPY for TABS, respectively. OBTS among derivatives under study shows the lowest corrosion density (0.54 6 muA/cm2) and the slowest corrosion rate (0.288 MPY). Also, the charg e transfer resistances and the double layer capacitances are 275.21 kO MEGA.cm2 and 7.0 muF.cm-2 for CBTS; 14.24 kOMEGA.cm2 and 26 muF.cm-2 f or DCBS; 54.15 kOMEGA.cm2 and 16 muF.cm-1 for TBBS; 0.96 kOMEGA.cm2 an d 83 muF.cm-2 for TABS, respectively. The weaker the electron donating inductive effect of derivatives is and the smaller the effect of ster ic hindrance is, the more the corrosion of brass coated steel cords in the acetonitrile solution of sulfenamide derivatives is prevented. Th e above results agree with that observed in the field of tire industry .