The role of Cu-based intermetallics on the pitting corrosion behavior of Sn–Cu, Ti–Cu and Al–Cu alloys

The aim of this study is to evaluate the effect of three different intermetallics; Cu6Sn5, Ti2Cu and Al2Cu, on pitting corrosion of Sn–2.8 wt.% Cu, Ti–5 wt.% Cu and Al–5 wt.% Cu as-cast alloys, respectively. Chill-cast and centrifuged-cast samples were subjected to potentiodynamic polarization corrosion tests in a sodium chloride solution at 25 °C. It was found that the intermetallic particles play an important role in the process of pitting corrosion. The results have shown that the pitting potentials (EPit) of all three alloys experimentally examined have been displaced about 10 mV (SCE) toward the nobler-side potential when compared with the corresponding corrosion potentials (ECorr). It was also found that the lamellar morphology formed by alternated solvent-rich/intermetallics phases, which characterizes the microstructure of any alloy examined, provides an enveloping effect giving rise to a protective barrier against corrosion. Other microstructural features associated with the ratio of anode/cathode areas for each alloy examined are also discussed.