chemical polishing process yields aluminum alloy workpieces having on the surface thereof an extremely thin oxide layer in the range of 10 to 50 angstroms which has been found to have no adverse effects on subsequent plating adhesion in fact aluminum alloy polished in accordance with the invention have been successfully plated after 6 to 8 months of storage table 1 below is illustrative of a conventional chemical polishing bath this prior art bath formula is taken from wernick amp pinner the surface treatment and finishing of alloys vol 1 1972 4th ed pp 122 126 smut is caused by lack of sufficient oxidizing power in the polishing bath the addition of sodium nitrate to the bath of the present invention is believed to maintain the oxidizing power at a level which eliminates both the formation of smut and pitting of the panel 39 s surface pitting is typically caused by a very low concentration of nitric acid table 2 illustrates the effect of adding sodium nitrate to the bath formulation over time while table 3 is illustrative of the preferred embodiment and practice of the invention it is to be noted that good results were obtained at each try while no additions of any bath constituent were made the only degradation in results occurred when the panel remained in the bath for a time greater than the preferred bath immersion period note in table 3 that no smut or pitting was observed on the test panels samples of wrought aluminum alloy 6061 t6 were degreased in 1 1 1 trichloroethylene and then treated in a preheated solution having the composition of 784 ml phosphoric acid 98 ml nitric acid 40 grams sodium.