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.