Effect of Nb Addition on Corrosion Resistance of U-6Zr Alloys

The fuel element plates in a research reactor can be exposed to an acidic, neutral, or alkaline environment based on its surroundings. This study aimed to investigate the effect of Nb addition on the corrosion properties of U-6Zr alloys in various environments. U-6Zr-xNb alloys (U-6Zr-2Nb, U-6Zr-5Nb, and U-6Zr-8Nb) with different Nb compositions of 2, 5, and 8 wt%, respectively, were prepared and cut into smaller pieces. The pieces were then mounted with chemical resin equipped with copper wire cables and metallography prepared by grinding using sandpaper with grit sizes ranging from 320 to 1200. The electrochemical corrosion tests used in this work were the polarization test and Tafel extrapolation method.

In the first step of corrosion testing, the corrosion potential and polarization resistance were measured using standard settings from a voltage range of −0.02 to 0.02 V with a scanning rate of 0.05 mV/s. In the next step, a destructive method, called the Tafel extrapolation method, was used. Corrosion tests were carried out on U-6Zr-xNb alloys (x = 2, 5, 8) under various environmental conditions using electrochemical methods. Polarization resistance test and Tafel extrapolation methods revealed that the U-6Zr-2Nb alloy exhibited good corrosion resistance in an acidic HNO₃ environment with a pH of 1.18. The best corrosion resistance of the U-6Zr-5Nb alloy was observed in demineralized water. Meanwhile, the U-6Zr-8Nb alloy showed the best corrosion resistance in an alkaline NaOH environment with a pH of 11.02. It can be concluded that the higher Nb composition added to U-6Zr alloys, the better their corrosion resistance in higher pH environments.