Dezincification of Brass in Sulfide Polluted Sodium Chloride Medium: Evaluation of the Effectiveness of 2-Mercaptobenzothiazole

Abstract

The present paper addresses the effectiveness of 2-mercaptobenzothiazole (MBT) in preventing the dezincification of brass in sulfide polluted 3.5% NaCl solution. The dezincification behaviour of brass in 3.5% NaCl solution containing 100-1000 ppm of sulfide ions and 1 x 10-6 to 1 x 10-3 M MBT was studied by potentiodynamic polarization, electrochemical impedance spectroscopy, current-time transient and accelerated leaching studies. The presence of sulfide ions in 3.5% NaCl solution has caused a significant increase in the extent of corrosion attack on brass. The inhibiting effect of MBT is markedly reduced in the presence of sulfide ions in the medium. The easy replacement of Cu-MBT complex by Cu2S film on the surface of brass is responsible for the inability of MBT to prevent corrosion attack in the presence of sulfide ions. The study concludes that the effectiveness of MBT in preventing the dezincification of brass is dependent on the concentration of the sulfide ions in the medium and the effectiveness is nullified at higher concentrations of sulfide ions.