Electrochemical properties and dissolution of UPd3 in nitric acid solutions

The electrochemical properties of URu3 intermetallic compound (IMC) in 0.5–8 M HNO3 solutions were studied by linear voltammetry and galvanostatic electrolysis. In 0.5–2 M HNO3, URu3 occurs in the passive state at potentials lower than +1.3 V (here and hereinafter, vs. SHE), and in 4–8 M HNO3, an anodic oxidation peak is observed at potentials from +1.0 to +1.2 V. This process, however, leads to IMC passivation and not to its dissolution. At potentials higher than +1.4 V, URu3 passes into the transpassive state and starts to actively dissolve. The principal possibility of electrochemical dissolution of IMC at potentials exceeding the transpassivation potential was demonstrated by galvanostatic electrolysis. The rate of uranium leaching during electrolysis depends to a greater extent on the current density than on the HNO3 concentration and reaches 35 mg cm–2 h–1 in 6 M HNO3 at a current density of 182 mA cm–2.