Corrosion Mechanism of Cu-9.4 Ni-1.7 Fe Alloy in 3.4 WT.% NaCl Solution with and without Sulfide Contamination

摘要

Corrosion products were developed on commercially available Cu-9.4 Ni-1.7 Fe alloy discs which rotated at 800 r.p.m. in 3.4 wt. % NaC1 solution with and without sulfide contamination for various lengths of time up to 10 days. The developed corrosion products were characterized with X-ray diffraction, SEM, and ESCA studies. Anodic and cathodic polarization curves were measured on the corrosion-product covered alloy surface as well as on the fresh surface to study the electrochemical behavior of the alloy. The results show that (i) the weight loss of the alloy during immersion in clean solution increases with time according to a parabolic rate law which is due to the mass-transfer limited anodic metal dissolution rate, and (ii) the cathodic oxygen reduction reaction on the corrosion-product covered alloy in the clean solution is controlled by the poor catalytic nature of the corrosion products; however, this catalytic capability is improved by the addition of sulfide during the formation of the corrosion products, thus a high corrosion current is obtained in sulfide-polluted 3.4 wt. % NaC1 solution. (Author)