Corrosion of iron in liquid uranium hexafluoride

Here is reported a dedicated and reliable experimental setup which has been designed to study the corrosive effects of liquid uranium hexafluoride (UF₆) on pure metallic iron at 80 C and 3 bars of pressure. Three corrosion tests have been carried out, ranging from several hundred to almost one thousand hours. No uniform corrosion was observed on early-stage samples. However, a nodule facies consisting in FeF₂ and UF_x (with 4≤x≤5) deposits is observed at the surface of the iron samples. These FeF₂ nodules grow with time and merge, leading finally to the formation of an almost continuous FeF₂ layer. The thickness of the layer over time seems to follow a parabolic kinetics law, finally reaching 15 μm after about one thousand hours of immersion in liquid UF₆. After the nodules have merged, many cracks can be observed in the FeF₂ layer, probably due to the growing stresses as the corrosion layer is formed. (authors)