The mechanism and kinetics of corrosion product release from stainless steel in lithiated high temperature water

The oxide films that develop on type 304 stainless steel in lithiated high temperature water are examined by scanning electron microscopy and Auger electron spectroscopy. The paper shows how the structure and morphology of the film can be manipulated by altering the level of corrosion products in the water, and demonstrates that the precipitated outer layer of iron-rich oxide crystals affords no protection against corrosion. The importance of outer layer precipitation in the mechanism of corrosion product release is discussed. It is shown, for example, how the apparent release of iron can be measured by radiotracing, even in experiments using corrosion product-saturated water where no net release can actually occur. The effects, on release, of physical parameters which influence the degree of saturation of the water are discussed. Such system effects must control release around an operating circuit such as a power reactor coolant. The development of a simple mathematical model demonstrates how such system effects can lead to apparently complicated kinetics for release.