Electrochemical And Metallurgical Behaviour Of Ductile Iron In Acidic, Basic And Saline Environments

Abstract

This research work presents the comparative study of the effect of some selected environments on the corrosion characteristics and accompanying changes in microstructure on ductile iron. In this study, the atmospheric corrosion of ductile cast iron immersed in acidic (2M H2SO4), basic (2M NaOH) and saline (3.5% NaCl) environments, which represents the major atmospheric environments in which metals are mostly subjected to while in service. The corrosion characteristics of ductile iron have been determined by current potential curves. To determine the corrosion rates, the anodic and cathodic Tafel regions extrapolating to corrosion potentials were used. The individual corrosion rates of ductile iron were evaluated for a time period of 600 seconds, 1mv/s scan rate and Tafel plot range of -250mv to 250mv. Each sample were dimensioned, polished, pickled in dilute HCL and rinsed with distill water, degreased with acetone followed by drying and then mounted for the potential dynamic tests. The results obtained reveal that corrosion of DI in 2M H2SO4 is (0.25699 mmpy), 2M NaOH is (0.025955 mmpy), 3.5% NaCl is (0.10396 mmpy) and distill water is (2.6447e-05 mmpy). The results obtained showed that corrosion rate in decreasing order is 2M H2SO4, 3.5% NaCL, 2M NaOH and lastly as expected distil water. The corrosion product morphologies of the DI showed the nodular matrix was gradually covered up as the corrosion rate increased. This work is important reference point for the corrosion effectiveness of ductile iron in major atmospheric conditions.