Residual contamination and corrosion on electrochemically marked uranium

Abstract Residual contamination and potential corrosion problems on uranium parts electrochemically marked with PHB-1 and PHB-1E electroetchants have been investigated using ion microprobe mass analysis (IMMA), scanning electron microscopy (SEM), and light microscopy (LM). The effectiveness of various solvent-cleaning sequences and the influence of the use of an abrasive cleaner were evaluated. The corrosion depths and chlorine distributions resulting from the electroetching process were determined. To meet the objective, the surfaces of uranium coupons, which had been processed according to production procedures for parts, i.e., machining, cleaning, marking, inspecting and coating with Shell Vitrea-29® oil, were studied. The greater surface wetting capability of the PHB-1E electroetchant solution relative to PHB-1 resulted in less localized corrosion at the point of attack which provided a more legible mark. Components of the electroetchants (aluminum, potassium and chromium) were found in the marked areas of both types of electroetched samples. Chromium, resulting from the corrosion inhibitor in the electroetchants, was found in the etched areas as well as on the coupon away from the electroetched areas. Depth profile data indicated that the major etching action (marking thickness) of the electroetchants penetrated to a depth of approximately 200 nm. Trace amounts of chlorine were present primarily within the first 65 nm of the marked surface. Comparison of the solvent rinsing sequences revealed that the most effective cleaning process included a degreaser, such as perchloroethylene, followed by a polar solvent, such as alcohol. Evaluation of the use of an abrasive cleaner on the electroetched areas indicates that this process removed residual contaminants, increased mark legibility and did not introduce significant residuals from the abrading material or cause significant surface damage.