The Effect of Dissolved Oxygen on the Oxidation of Zircaloy-2 by Steam

Predetermined amounts of oxygen were added to Zircaloy-2 by three methods which were expected to give widely different distr ibutions of the oxygen in the metal. Subsequent oxidation of these specimens in steam showed that increases in the oxidation rate could be ascribed largely to the inhomo-geneous distr ibution of the oxygen. The closer a homogeneous oxygen distr i-bution was approached, the closer the oxidation rate approached that of low-oxygen material. If the oxygen distr ibution in the surface was uniform, the presence of an oxygen gradient through the specimens did not result in an increase in the oxidation rate. Dur ing the ox idat ion of many z i rconium al loys in oxygen, steam, or carbon dioxide, a t rans i t ion occurs f rom an approx imate ly cubic rate law to a more rap id l inear re lat ionship. This t rans i t ion is appar-ent ly due to the breakdown of the protect ive oxid