Anodic dissolution of vanadium metal in NaCl-KCl melts

1 Anodic dissolution of vanadium metal in NaCl-KCl melts 

At the first stage a series of experiments was performed to study the kinetics of anodic dissolution of vanadium in a high-temperature NaCl-KCl electrolyte that initially did not contain vanadium ions. The measurements were conducted between 698 and 859 °C. Potentiodynamic studies were carried out with the potential sweep rate varied from 50 to 3000 mV/s and the potential range from -1.8 to -1.4 V. 

The stationary potential ( stat) of vanadium in NaCl-KCl equimolar mixture is equal to -1.955, -1.934, and -1.920 V at 698,771, and 859 C, respectively. Taking into account that vanadium(II) ions are formed as a result of metal corrosion [11] and using the diffusion coefficients (see below) and the approximate thickness of diffusion layer 5 = 0.01 cm, we estimated the corrosion currents (/con-) frooi Equation 4.5.1  

The corrosion current values were also determined from linear voltammograms using a known technique [12]. The results obtained by these different methods agree well and show that the corrosion current do not exceed 3-10 A/cm. Thus, the contribution of vanadium corrosion in the anodic process in the studied range of current densities (higher than 0.01 A/cm ) can be neglected. 

In case of the mass transfer-controlled processes the dependence of potential on anodic current density (in the region of constant activity coefficients) can be described [13] as  

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