Anodic film growth and silver enrichment during anodizing of an Mg-0.6 at.% Ag alloy in fluoride-containing organic electrolytes

Binary Mg-Ag alloys are of interest as antibacterial biodegradable materials. In the present work, the behaviour of silver during galvanostatic anodizing of a sputtering-deposited Mg-0.6 at.% Ag alloy in a fluoride/glycerol electrolyte containing 5 or 60 vol.% water was investigated. Similar alloy compositions have been shown to have potential as biomaterials in in-vitro tests. The resultant barrier-type anodic films were examined using scanning and transmission electron microscopies, glow discharge optical emission spectroscopy and Rutherford backscattering spectroscopy. The films were shown to be nanocrystalline and to contain oxide and fluoride species, with O:F atomic ratios dependent on the amount of water in the electrolyte. Silver species were incorporated into the films, accompanied by loss of silver species to the electrolyte. Notably, silver was enriched in a ≤ 6 nm thick alloy layer, to concentration of at least 12 at.%.