Corrosion behavior of a non-equiatomic CoCrFeNiTi high-entropy alloy: A comparison with 304 stainless steel in simulated body fluids

•We successfully designed and synthesized a new type of non-equiatomic Co40Fe35Cr16Ni8Ti1 HEA, which has excellent corrosion resistance in the human body fluids, and also has the mechanical properties required for coronary stent materials.•Hank’s simulated body fluid was used to simulate human environment, and there are currently few studies on the corrosion resistance of high-entropy alloy in the human environment.•Our designed Co40Fe35Cr16Ni8Ti1 HEA has less Ni content than common HEA, and we added Ti into our high-entropy alloy, which can make it have better biocompatibility, corrosion resistance and mechanical properties. A new type of non-equiatomic Co40Fe35Cr16Ni8Ti1 HEA was designed and synthesized, and its corrosion resistance was compared with 304 SS in Hank's simulated body fluids to verify its feasibility as an alternative for existing coronary stent materials. Electrochemical tests showed that the corrosion current density of Co40Fe35Cr16Ni8Ti1 HEA was 10−6 in order of magnitude, which was about 1/6 of that of 304 SS, and the impedance value of Co40Fe35Cr16Ni8Ti1 HEA was 105 in order of magnitude, which was about 7 times that of 304 SS. Scanning electron microscopy testing showed that after 120 h of continuous salt spray corrosion, the surface of 304 SS showed obvious corrosion morphology compared with Co40Fe35Cr16Ni8Ti1 HEA, and it was corroded with clear grain boundaries. After 6 h of potentiostatic polarization, a passive film was formed on the surfaces of Co40Fe35Cr16Ni8Ti1 HEA and 304 SS respectively, and the composition of the passive film of the two materials was analyzed by X-ray electron spectroscopy. Compared with 304 SS, the passive film formed on Co40Fe35Cr16Ni8Ti1 HEA is rich in Co and Cr elements, and the high Content of Cr and Ni makes Co40Fe35Cr16Ni8Ti1 HEA have higher corrosion resistance in Hank simulated body fluid. The high content of Fe2+ oxide in the passive film is the main reason why 304 SS is less resistant to corrosion than Co40Fe35Cr16Ni8Ti1 HEA in Hank's simulated body fluid.