Galvanic corrosion associated with Al–B4C composites/SS304 and Al–B4C composites/AA6061 couples in NaCl and H3BO3 solutions

By Han, Yu-Mei; Gallant, Danick & Chen, X.-Grant
Published in Electrochimica Acta NULL 2013

Abstract

Al–B4C composites are neutron absorber materials utilized in the nuclear industry that are often assembled to structural materials AA6061 or SS304, which increases the likelihood of galvanic corrosion, especially under wet storage conditions. This study investigates the galvanic corrosion behavior that may occur between Al–B4C composites and AA6061 or SS304 in NaCl and H3BO3 solutions using a zero resistance ammeter (ZRA). The effects of dissimilar materials (e.g., B4C content), immersion solution, and ratio of the coupled material areas are reported. In the NaCl solution, depending on the nature of the coupling agent (SS304 or AA6061), the composite or base alloy always acts as an anode and the measured galvanic currents are directly proportional to the cathode area. In contrast, in the H3BO3 solution, the composites preferentially dissolve in the presence of SS304, while AA6061 protects the metal matrix composites from dissolution. Although galvanic corrosion is controlled by oxygen diffusion at the cathode in both NaCl and H3BO3 solutions, its intensity is appreciably lower in the H3BO3 solution than in the NaCl solution. The B4C content is also found to play a key role in galvanic corrosion; its influence is modulated by the solution composition and the materials to which the composite is galvanically coupled.

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