The Effect of Surface Treatments and Electrochemical Methods on the Pitting Potentials of Zirconium in Chloride Solutions

The effect of surface treatments and electrochemical methods on the corrosion (Er), pit nucleation (Enp), and critical pitting (Ecp) potentials have been investigated for zirconium in aqueous chloride solutions. Specimens were tested in the mill annealed, SiC abraded, chemical polished, electropolished, air annealed, and vacuum annealed conditions. Er was determined by open circuit, nulling, and polarization methods. Enp was determined by potentiostatic, potentiostep, and potentiodynamic methods. Ecp was determined by a potential back-step and a scratch method. The pitting morphology at the surface show radal pit growth. Er and Enp depend on the surface preparation and environment, but Ecp does not depend on surface preparation or previous potential history. The SiC abraded surface yields the most reproducible pitting corrosion data and behaves similarly to the as-received mill annealed surface condition. The poteniostatic, scratch and back-step techniques yield the same pitting potential.