Luminescence during the anodization of zirconium

► Anodization of zirconium in (COOH)2 and H4SiW12O40 water solutions. ► Galvanoluminescence (GL) is related to the existence of flaws in oxide coating. ► Spectral characterization of GL shows wide GL bands mostly in the visible region. ► OES reveals spectral lines from the electrolyte during PEO in H4SiW12O40. ► OES reveals lines from the substrate and the electrolyte during PEO in (COOH)2.