The Røcle of hydrogen in the high‐temperature corrosion of zirconium and its alloys. I. The effect of cathodic polarization on corrosion in water at 325°

Abstract

Binary zirconium alloys and Zircaloy 2 have been corroded in water at 325°c with and without cathodic polarization. In some cases polarization can increase hydrogen uptake or reduce the protective character of the oxide films as assessed by capacity measurements. Alloying elements significantly influence both effects, but comparison of the alloys shows no systematic relation between their hydrogen uptakes and the loss of protective character of their films. Films formed in a previous period of unpolarized corrosion are damaged when polarized at 325° and at room temperature. Possible explanations of the effects of hydrogen and of alloying elements are suggested.

A Mechanism for the Effect of Heat‐Treatment on the Accelerated Corrosion of Zircaloy‐4 in High Temperature, High Pressure Steam

“…In arguing that hydrogen migration into the oxide leads to accelerated corrosion, the present model resembles some aspects of previously suggested (15,16) mechanisms for various accelerated corrosion processes in zirconium and other alloys. However, these earlier studies were not focused on heat-treatment effects or on the particular accelerated corrosion phenomenon which occurs with Zircaloy in high temperature, high pressure steam 9 A more recently proposed (17) model for nodular corrosion based on cathodic depolarization at intermetallic particles is in some respects opposite to the mechanism suggested here.…”