Abstract
The protective merit of electrodeposited coatings, mainly nickel, on uranium has been assessed in air at 60° and 80% R.H. over long term exposure on a weight-gain basis. Factors likely to influence performance have been studied and include surface preparation, type of bath, coating thickness, supplementary coatings, post-deposition treatments, etc. Results indicate the importance of surface preparation, a satisfactory degree of protection being obtained consistently only on etched uranium surfaces. It also appears to be essential to maintain a wetting agent in the nickel-plating bath and to keep coating thickness above a certain minimum.
With the best coatings there is no detectable weight gain even after six months exposure while with the worst not only is there no protection but the corrosion rate of the underlying uranium is enhanced. In the intermediate range of performance, most coatings behave well initially but the protective merit deteriorates slowly or more rapidly with time of exposure.
Protective merit deteriorates very rapidly if the coating (not pore-free) is unbonded whilst breakdown rates of well-bonded coatings may be almost imperceptible at low porosity levels. Highly porous coatings, such as are frequently obtained at low thickness, offer little protection at an early stage of exposure even when well bonded.
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