Tritium sorption and chemical and topographical properties of a stainless steel surface modified with chromium

The surface modification of stainless steel has been attempted by a method of electrodeposition of chromium combined with thermal oxidation. The surface layer formed by the partial oxidation of chromium electrodeposited onto a stainless steel surface has been found to be markedly effective in depressing tritium sorbability (ad- and ab-sorbability). The surface layer was determined to be 3 μm in thickness; it was constituted of a 0.1 μm thick outer layer of Cr(III) in a Cr2O3-like state and an inner layer of metallic Cr(0). The surface was observed to be very smooth on a nanometer scale. From these observations, it was inferred that the depression of tritium sorbability was attained not only by chemical stabilizing of the topmost surface due to the formation of a Cr2O3-like state, but also by smoothing on a nanometer scale and probably densifying of the surface layer through the partial oxidation. (orig.)