Sulfide Induced Intergranular Corrosion of Copper in Salt Water Containing Benzotriazole

This paper investigates the effect of pretreatment with benzotriazole on the corrosion of copper in sulfide polluted salt water. The treatment of copper in the presence of benzotriazole under a mild oxidizing potential reveals the remarkable inhibition efficiency of BTAH reflected in a passive current of less than 0.1 mu A cm(-2) after one hour. Upon injection of 10(-3) M HS-, a rapid increase in current to about 200 mu A was obtained. The current jump seen after injection of sulfide ions is due to localized intergranular corrosion as shown by the scanning electron microscopy (SEM) examination. Copper suffered only localized corrosion occurred at the grain boundaries while the grain surfaces remained well protected. Under this condition, sulfur was detected using energy dispersive spectroscopy (EDS) at the grain boundaries, but not on the grain surfaces. X-ray photoelectron spectroscopy revealed the presence of sulfide ions and BTAH on the corroded surface.