Pitting corrosion of artificially aged T6 AA2024/SiCp composites in 3.5wt.% NaCl aqueous solution

The pitting corrosion behavior of the underaged (UA), peakaged (PA) and overaged (OA) T6 AA2024/0, 8, 14, 19, 24 vol.% 40 μm SiCp(particles) composites was studied. The processing route used for the materials was the compocasting technique. Corrosion potentials (Ecor), pitting potentials (Epit) as well as protection potentials (Eprot) were extracted from Double Cycle Polarization (DCP) curves contacted in aerated 3.5 wt.% NaCl aqueous solution. In addition 40 days immersion tests carried out and weight loss curves as well as total pit depth measurements were acquired. Pitting initiation and propagation as the main corrosion mechanism was driven by the aging kinetics which is ruled by the reduction in the retained vacancy concentration and at the same time by the increase in dislocation density as SiCp volume fraction increases. Thus, alteration in pitting behavior among composites of different SiCp content took place, although their ageing status was exactly the same.