Surface passivation on precipitated Ti-containing multi-principal element alloy subject to metal aging

Surface passivation on precipitated Ti-containing multi-principal element Alloys (MPEA) is studied in saline solutions with different concentrations and different temperatures. The selected system alloy is Al 2 Ti 5 Fe 53 Ni 35 Cu 5 at.% which has been solution heat treated at 530 °C for 3h (CONFIG 2) and for 10h (CONFIG 3) from the as-received configuration (CONFIG 1). The potentiodynamic polarization (PDP) test specifies that the corrosion resistance of aged Ti-containing alloys decreases as a function of aging time, while the as-received configuration reflects a nobler behavior. Microcapillary technique supports these findings by probing FCC grain passivity at the microscale level aiming at the core of the grain. Local PDP reveals that the potential of CONFIG 1 grain is sensitive to the chloride concentrations whereas it is almost independent in the remaining configurations suggesting that the weakest link is elsewhere. Profilometer analysis shows that microgalvanic processes take place between grains and boundaries having both anode- and cathode-like behavior interchangeably.