Virgilio Pereira Ricci, Emerson Cortez Gallego Campos, Victor Hugo Mafra Monfredo Ferreira, Rafael Magalhães Triani, Guilherme Zepon, Francisco Gil Coury, Eric Marchezini Mazzer, Guilherme Yuuki Koga
This study explores the corrosion behavior of a nonequiatomic Ni60Cr15Co15Ti5Al2.5Nb2.5 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 mVSCE and an increase in corrosion current density i corr to 2.7 μA/cm2. 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 mVSCE, a significant reduction in i corr to 7.1 × 10-2 μA/cm2, and an increase in pitting potential (E pit) from +413 mVSCE to +495 mVSCE. Electrochemical impedance spectroscopy (EIS) further confirmed enhanced passivity through a reduction in effective capacitance (from 3.2 to 2.6 μF/cm2) and an increase in polarization resistance (from 960 to 1084 kΩ·cm2). However, excessive aging (>50 h) may trigger a secondary LOP. An optimal aging window (30-50 h) yields a stable and protective passive film.