Corrosion Behavior of B4C/6061Al Neutron Absorber Composite in Different H3BO3 Concentration Solutions

In this study, electrochemical corrosion tests, full-soak corrosion tests and associated microstructure analysis were conducted to investigate the corrosion behaviors of B4C/6061Al neutron absorber composites (NACs) manufactured by powder metallurgy method in solutions having different boric acid (H3BO3) concentrations (500, 2500 and 10,000 ppm). In electrochemical corrosion tests, B4C/6061Al NACs demonstrate the highest (short-term) corrosion resistance in the 2500 ppm H3BO3 solution. While for full-soak corrosion tests, the B4C/6061Al NACs show the highest (long-term) corrosion resistance in the 500 ppm H3BO3 solution. This difference is found to be mainly due to the formation of different surface morphologies during these two different corrosion tests. As noticed, a layer of Al(OH)(3) was formed on the composite surface during full-soak corrosion tests, but it cannot be found in the electrochemical corrosion tests. The full-soak corrosion mechanism of the B4C/6061Al NACs in the H3BO3 solution is found to be primarily determined by the dynamic balance between the formation and dissolution rates of the oxide film, which is mainly controlled by the density of H+ ions in the solution.