Effects of benzotriazole on the localized corrosion of copper nickel alloys in sulfide polluted salt water

Benzotriazole (BTAH) affects the localized corrosion of Cu10Ni alloy in 3.4% NaCl salt water containing 2 ppm sulfide ions. BTAH concentrations > 5 × 10-4 M imparted corrosion inhibiting efficiency that increased with its concentration. On the other hand, a concentration of 10 -4 M BTAH acted as a promoter of pitting corrosion of the alloy in the above medium. The results of optical and scanning electron microscopy could be rationalized on the basis of competitive adsorption of BTAH and sulfide ions on the alloy surface, the simultaneous formation of the protective cuprous oxide and the nonprotective copper sulfide and the incorporation of sulfide ions in the anion deficient lattice structure of Cu2O. The presence of the above phases was identified in the x-ray diffraction spectra of the corrosion products.