Cr<sub>40</sub>Co<sub>40</sub>Ni<sub>20</sub> Multi-Principal Element Alloy Outperforms Inconel 625: A Passivation and Corrosion Resistance Study in Chloride Media
Victor Hugo Mafra Monfredo Ferreira, Virginie Roche, Margarita Díaz Ramos, Gustavo Bertoli, Alberto Moreira Jorge, Jean-Claude Leprêtred, Walter José Botta, Francisco Gil Coury, Guilherme Yuuki Koga
Abstract
The corrosion resistance of the Cr 40 Co 40 Ni 20 multi-principal element alloy was evaluated in chloride-rich electrolyte. The alloy was synthesized via vacuum induction melting and subjected to thermomechanical processing, including homogenization at 1100 °C, rolling to a final thickness of ∼1 mm, and recrystallization heat treatment at 1050 °C for 30 min. Structural characterization using X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction confirmed a refined and homogeneous single-phase microstructure with an average grain size of ∼20 μm. The corrosion behavior was analyzed through cyclic potentiodynamic polarization and electrochemical impedance spectroscopy in 0.6 M and 0.1 M NaCl solutions. The results revealed that Cr 40 Co 40 Ni 20 alloy is corrosion-resistant, forming a highly protective and stable passive film. The polarization resistance was measured at 200 kΩ·cm 2 in 0.6 M NaCl, significantly higher than the ∼120 kΩ·cm 2 observed for Inconel 625, indicating superior passivation. Electrochemical impedance spectroscopy analyses demonstrated a capacitive-like response with phase angles close to −85° and a resistivity at metal/oxide interface profile suggesting an insulator-like passive layer with a resistivity of 10 9 Ω·cm, outperforming Inconel 625.