Potential and Hydrodynamic Effects on the Formation and Dissolution of Tungsten Oxide Film in Alkaline Solution

초록

Anodic dissolution of tungsten has been used for electropolishing, electrochemical machining and etc. Tungsten is covered with the native oxide film(WO3) which suppressed the metal dissolution. During anodic etching of tungsten, tungsten oxide is initially formed on the surface and transformed into dissolving species, WO42- because WO3 is highly unstable in alkaline solution. Consideration of electroneutrality on the dissolving tungsten surface suggests that the removal of WO42- is important to reach a high dissolution rate. However, it was observed that tungsten surface is locally covered with the oxide film during active anodic dissolution. This work is intended to investigate the potential and hydrodynamic effects on the formation of tungsten oxide during anodic dissolution. Linear sweep voltammetry was employed to identify the tungsten dissolution behaviors and, surface morphology and compositions were investigated with SEM and EDX.