Abstract
This study explores the corrosion behavior of a nonequiatomic Ni(60)Cr(15)Co(15)Ti(5)Al(2.5)Nb(2.5) high-entropy alloy (HEA) subjected to thermal aging. Electrochemical testing in 3.5 wt% NaCl solution revealed that short-term aging (≤1 h) induces a loss of passivation (LOP), marked by a corrosion potential drop to -260 mV(SCE) and an increase in corrosion current density (i (corr)) to 2.7 μA/cm(2). In contrast, prolonged aging (≥10 h) promotes a recovery of passivation (ROP), driven by microstructural elemental redistribution. This recovery is evidenced by a positive shift in corrosion potential to -125 mV(SCE), a significant reduction in i (corr) to 7.1 × 10(-2) μA/cm(2), and an increase in pitting potential (E (pit)) from 413 mV to 495 mV. Electrochemical impedance spectroscopy (EIS) further confirmed enhanced passivity through a reduction in effective capacitance (from 3.2 to 2.6 μF/cm(2)) and an increase in polarization resistance (from 960 to 1084 kΩ·cm(2) ). However, excessive aging (>50 h) may trigger a secondary LOP. An optimal aging window (30-50 h) yields a stable and protective passive film.