Influence of electropolishing and anodic oxidation on morphology, chemical composition and corrosion resistance of niobium

Abstract

The work presents results of the studies performed on electropolishing of pure niobium in a bath that contained: sulphuric acid, hydrofluoric acid, ethylene glycol and acetanilide. After the electropolishing, the specimens were subjected to anodic passivation in a 1 mol dm- 3 phosphoric acid solution at various voltages. The surface morphology, thickness, roughness and chemical composition of the resulting oxide layers were analysed. Thusly prepared niobium samples were additionally investigated in terms of their corrosion resistance in Ringer's solution. The electropolished niobium surface was determined to be smooth and lustrous. The anodisation led to the growth of barrier-like oxide layers, which were enriched in phosphorus species. © 2014 Elsevier B.V.Russian Foundation for Basic Research, RFBR: 13-08-96007; Ural Branch, Russian Academy of Sciences, UB RAS: 12-T-2-1009This work was supported by the Polish Ministry of Science and Education under the “Diamond Grant” programme, research project no. DI 2012 024142 . We acknowledge also the partial support of the Ural Division of the Russian Academy of Sciences (Project 12-T-2-1009 ) and the Russian Foundation for Basic Research (Project 13-08-96007 )