Potassium fluoride,anhydrous
           Potassium fluoride,extra pure
           Potassium fluoride,Granular
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Some studies suggest that the mechanism of Zr dissolution in Hydrofluoric Acid is altered by HNO3 and that the nitric acid is simultaneously reduced along with Zr dissolution. Hence these results may not be directly applicable to nitric acid free systems. HF being a weak acid dissociates to a limited extent, and can form multiple species as the three equilibrium reactions given below.

HF ? H++F-

HF+F-?HF2-

HF+HF2-?H2F3-

The equilibrium constants respectively are K1 = 6.84 × 10-4, K2 = 5, and K3 = 0.58.

In this study, we investigate the effect of varying the concentration of Hydrofluoric Acid on Zr dissolution. A rotating disk Zr electrode was used in a conventional three electrode cell with Ag/AgCl (in 3.5 M KCl) and Pt wire as reference and counter electrode respectively. Hydrofluoric Acid concentration was varied from 5 mM to 200 mM, 0.1 M Na2SO4 was used as the supporting electrolyte in all the experiments. The electrode was rotated at 900 rpm to minimize the mass transport limitations. Potentiodynamic polarization experiments were conducted starting at 250 mV below open circuit potential and ending at 2500 mV above OCP on the anodic side. In solutions with HF, the scan rate was maintained at 2 mV/s concentration of 50 mM or less. 

When at 100 mM and 200 mM Hydrofluoric Acid, the scan rates were  increased to 20 mV/s since a black film formed on the electrode at lower scan rates and caused a sudden change in current values. The results are following: the anodic polarization curves indicating that the active and passive regimes are clearly visible in all the HF concentrations studied here. The potential the current in the cathodic and anodic regime are presented, with the current in logarithmic scale. The corrosion currents were estimated by extrapolating the cathodic and anodic branches. Thepeak current value increases along with an increase in HF concentration. When it reached higher concentration, the peak potential location shifts to more positive values. It shows that HF plays an important role in the reaction.