Corrosion Morphologies of Aluminum-Based Materials in Solutions Containing Nickel or Cobalt Cations

摘要

Corrosion morphologies of a 6092-T6 Al metal-matrix composite (MMC) reinforced with boron carbide (B4C) or silicon carbide (SiC) particulates as well as a Al-2%Cu alloy in solutions Containing 1 mM Ni(NO_3)_2 or Co(NO_3)_2 were examined with scanning electron microscopy (SEM) and energy-dispersive X-ray analyses (EDXA). SEM indicated that precipitates formed on the surfaces of the MMCs and the Al-2%Cu alloy after prolonged immersion in the Ni(NO_3)_2 or Co(NO_3)_2 solutions. EDXA indicated that the precipitates contained Ni or Co elements. SEM also suggested that localized corrosion of the MMCs may be inhibited in the Ni(NO_3)_2 or Co(NO_3)_2 solutions without chloride ions but may be accelerated in the Ni(N_3)_2 or Co(NO_3)_2 solutions added with chloride ions. X-ray diffraction (XRD) experiments suggested that the precipitates may be Al-Ni or Al-Co hydrotalcite-like compounds.