The effect of heavy metal ions on the localized corrosion behavior of steels

The work presented in this paper deals with the investigations on the effect of heavy metal ions, e.g., Cu and Ni, on the localized corrosion behavior of carbon steel and SS 316L under different experimental conditions. The important experimental conditions which include the nature of aqueous medium, metal ion concentration, temperature, pH and flow condition have been taken into account. Immersion tests of 1, 6 and 12 month duration were carried out to determine the effect of metal ions on the corrosion rate of steels. Electrochemical technique like free corrosion potential measurements, has been carried out to investigate the role heavy metal ions on the corrosion behavior of carbon steel and SS 316L. The effect of heavy metal ions on the corrosion behavior of carbon steel is quite pronounced and follows interesting trends. The results of immersion tests in distilled water under both static and dynamic conditions show a decrease in the corrosion rates of carbon steel in presence of higher concentrations of metal ions. In seawater, the corrosion rate of carbon steel is affected significantly only at 100 ppm of metal ion concentration. Under different experimental conditions the corrosion rate of 316L is unaffected in presence of metal ions. The results of immersion tests find support from free corrosion potential measurements. Under controlled laboratory conditions, there is no evidence of localized attack in presence of different concentration of metal ions.