Electrochemical Behavior of Flame‐Sprayed Sc‐Doped AlCoCrFeMo High‐Entropy Alloy Coatings in 3.5% Sodium Chloride Solution

This study presents the electrochemical behavior of flame‐sprayed scandium (Sc)‐doped high‐entropy alloy (HEA) coatings by varying Sc at 0.1, 0.3, and 0.5 wt% to AlCoCrFeMo (referred to as HEA‐Base for undoped Sc, HEA‐Sc0.1, HEA‐Sc0.3, and HEA‐Sc0.5, respectively). The coatings were exposed to 3.5 wt% aqueous sodium chloride solution, simulating a saline water environment at room temperature. The corrosion behavior of HEA coatings was examined using electrochemical methods, including open‐circuit potential, potentiodynamic polarization curves, and electrochemical impedance spectroscopy. Electrochemical analysis showed that the HEA‐Sc0.3 coating exhibited a higher corrosion potential and lower corrosion current density than the HEA‐Base, HEA‐Sc0.1, and HEA‐Sc0.5 coatings, indicating superior corrosion resistance. The addition of Sc enhanced the corrosion resistance of Sc‐doped HEA coatings relative to HEA‐Base, resulting in a reduction in the corrosion rate of approximately 37–74%. This enhancement is attributed to the formation of stable passive oxide layers, such as Cr ₂ O ₃ , Al ₂ O ₃ , and Sc ₂ O ₃ , due to the incorporation of Sc into the HEA matrix. HEA‐Base exhibited pitting, whereas Sc‐doped HEA coatings showed distinct corrosion patterns, with Al–Sc‐rich phases being attacked. Cr‐rich and Mo‐rich phases remained unaffected. These results suggest that incorporating small amounts of Sc into AlCoCrFeMo HEA coatings significantly improves their corrosion resistance.