Immersion corrosion behavior, electrochemical performance and corrosion mechanism of subsonic flame sprayed FeCoCrMoSi amorphous coating in 3.5% NaCl solution

Abstract

A FeCoCrMoSi amorphous coating (AC) was fabricated on Ti6Al4V alloy (TA) by subsonic flame spraying (SFS) technique, which was used to improve its corrosion resistance. The morphology, element distribution and chemical composition of obtained coating were analyzed using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X–ray Fluorescence (XRF), respectively, and its amorphous structure was confirmed by X–ray diffraction (XRD). The immersion corrosion behavior and electrochemical performance of FeCoCrMoSi AC immersed in 3.5% NaCl solution for the different days were systematically investigated, and the corrosion mechanism of amorphous structure was also discussed by the model of passive film. The results show that the FeCoCrMoSi AC exhibits the dense amorphous structure, which is beneficial to improving the anti–corrosion performance of TA. The potentiodynamic polarization curve (PPC) and electrochemical impedance spectroscopy (EIS) indicate that the FeCoCrMoSi AC with the lowest icorr of 1.479 × 10−6 A·cm−2 immersed for 60 days has the largest capacitor loop diameter of 7.53 × 105 and charge transfer resistance Rct of 4.31 × 104 Ω, showing the highest comprehensive corrosion resistance. The mechanism of corrosion resistance is contributed to the Cr–rich passive film, which is further stabilized by the addition of Mo.