Surface passivation characteristics of Cantor alloy using dynamic electrochemical impedance spectroscopy

• The microstructure and passivation behavior of high-entropy alloys are investigated • Polarization studies revealed corrosion characteristics under applied potential • Dynamic electrochemical impedance spectroscopy demonstrated passivation behavior • High-entropy alloy exhibited accelerated corrosion at potential exceeding -0.186 V • Alloying elements, mainly of Cr and Mn, contributed to the passive characteristics High-entropy alloys (HEAs), which consist of multiple elements with equiatomic concentrations and a single FCC crystal structure, have garnered attention compared to conventional metals and alloys due to their superior performance and enhanced corrosion resistance. The presence of multiple elements substantially influences the corrosion characteristics and significantly affects the formation of the passive layer in the corrosive atmosphere. In the present work, polarization studies were performed to understand the corrosion characteristics of the alloy, and electrochemical impedance spectroscopy (EIS) with varying applied potentials, derived from the polarization curve, called dynamic EIS (DEIS), was used to elucidate the passivation characteristics of the wrought Cantor high-entropy alloy. The polarization and DEIS results, along with equivalent circuit curve-fitting analysis of the Cantor high-entropy alloy, revealed variations in capacitive loop diameters and charge transfer resistance corresponding to passivation characteristics until the applied potential reached -0.266 V vs SCE, after which breakdown occurred with transpassive characteristics when the applied potential exceeded -0.206 V vs SCE. The presence of alloying elements played a crucial role in the formation and breakdown of the passive layer. This phenomenon has been extensively investigated through morphological and X-ray photoelectron spectroscopy studies.