Electrochemical surface nitriding of zirconium in LiCl–KCl–Li3N systems

Electrochemical surface nitriding of zirconium has been investigated in LiCl–KCl–Li3N systems. From the XPS results, ZrN was formed on the outermost part of the Zr electrode surface when potentiostatic electrolysis was conducted at 1.0 V (versus Li+/Li), the reaction scheme of which was expressed as:N3−=Nads+3e−, Nads+Zr=ZrN.It was also found, from the results of XPS analysis, that the thickness and nitrogen concentration of the nitride layer increased as the applied potentials were made more positive. By comparing the cyclic voltammograms of the nitrided zirconiums prepared by the electrochemical nitriding process and the plasma nitriding process, the two anodic dissolution potentials in the LiCl–KCl melt at 723 K were almost the same at 2.2 V. This indicated that the corrosion resistance property of the nitrided layer formed by electrochemical nitriding was identical to that formed by plasma processing.