Cavitation-corrosion Behaviour of Nodular Cast Iron in Aqueous Environments

Abstract

The cavitation corrosion behaviour of nodular cast iron in the Arabian Gulf Seawater and in distilled water was studied using ultrasonically induced cavitation facility. In order to investigate the mechanism of cavitation of cast iron, the loss in weight and the corrosion current were measured under cavitation conditions in the presence and absence of applied cathodic protection as well as under static conditions. Potentiodynamic polarization experiments were conducted along with polarization resistance measurements to determine the electrochemical corrosion rate (K). The results indicate that K under cavitation conditions is very low, amounting to less than 0.001% of the erosion-rate (W) in all tested conditions. Cathodic protection was found to decrease(W) by about 25%. SEM examination revealed that the mode of material removal was by ductile tearing and brittle failure. The results indicate that the electrochemical factor has an enhancing effect on the mechanical damage. However, it is concluded that cavitation-erosion of nodular cast iron is essentially controlled by mechanical factors.