The pitting corrosion of zirconium and zirconium-niobium alloys in sulphate solutions containing chlorides at 300–373 K

Abstract

The effect of temperature on the pitting corrosion of zirconium immersed in sulphate solutions containing chloride was investigated using the scratch method at 300–373 K. The scratch method measures the re-passivation potential E r, representing the potential below which pits re-passivate. In potentiokinetic measurements, the re-passivation potentials were always more active than the pit nucleation potential E p above which pits nucleate. Pit nucleation potentials were measured by potentiokinetic and potentiostatic methods. Temperature does not affect E r when zirconium is immersed in 1 N KCl, but affects E r slightly when SO 4 2- ions are present in the solution. At 80 °C (353 K), E r decreases linearly with increasing Cl - ion content, but increases noticeably when SO 4 2- ions are present. The E r values of zirconium and Zr-Nb alloys are approximately equivalent when immersed in a 1 N KCl solution.