Evaluation of Localized Corrosion of Zirconium in Acidic Chloride Solutions

Zirconium is prone to localized corrosion in acidic chloride (Cl–) solutions contaminated by oxidizing ions, such as ferric or cupric ions. This tendency can be reduced by ensuring that the zirconium surface is clean and smooth. The effect of surface condition on localized corrosion of zirconium in acidic chloride solutions was predicted using potentiodynamic polarization scans. Predictions were confirmed by mass-loss tests on various combinations of surface finish and acid concentrations. A real-time indication of localized corrosion was derived by monitoring electrochemical noise produced between two similar electrodes immersed in an acidic chloride solution. Electrochemical noise monitoring correlated well with predictions from the potentiodynamic polarization and mass-loss experiments. Electrochemical noise results showed a more anodic potential caused by ferric ion (Fe3+) contamination might be necessary for localized corrosion but that it was not a sufficient condition. A clean zirconium surface reduced localized corrosion of zirconium.