Resin-bonded bridges may replace missing teeth and act as splints in periodontal treatment. The objective of this study was to investigate the etch pattern after electrolytic etching of selected Co-Cr alloys in hydrochloric acid and to assess the changes in alloy composition after different etching times. The alloys investigated were Vitallium, Wironit, Wironium, Nobilium Hard, and Niranium NN. Alloy specimens were electrolytically etched in a hydrochloric acid solution for 1, 2, 5, and 10 min. The etched specimens were examined in a light microscope and a scanning electron microscope (SEM). Different etching patterns were revealed in the various alloys. Microprobe analyses after the etching of Vitallium showed generally that Co was released and that Cr content increased at the surface.

Etching patterns of Co-Cr alloys for bonded cast restorations
Ekstrand K, Ruyter IE
J Dent Res. 1987 Sep; 66 (9): 1479-84