The electrochemical corrosion behavior of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy with different initial microstructures

Abstract

The corrosion behavior of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy with different initial microstructures was investigated by conducting a series of electrochemical tests. Based on the experimental data, the effects of NaCl solution concentration and corrosion time on the electrochemical polarization curves, corrosion rates, electrochemical impedance spectroscopy (EIS), and impedance of the alloy with two initial microstructures were analyzed. The assessment of the corrosion current density (Icorr) and corrosion rate (CR) for the alloy under different corrosion conditions reveals a general pattern of initial decrease followed by increase in their values with extended corrosion time and elevated solution concentration, whereas the capacitive reactance arc exhibits an opposite trend. For alloys with initial equiaxed microstructures, the Icorr value is 0.1892 μA/cm2, and the CR value is 0.000413 mm/year; these values are lower than those of 1.298 μA/cm2 and 0.002842 mm/year for alloys with initial lamellar microstructures. Whereas the capacitive reactance arc and the impedance value are greater for the titanium alloy with initial equiaxed microstructure. Based on the adsorption kinetics principles, the effects of temperature on corrosion rate of alloys with different initial microstructures at a consistent concentration were analyzed. Compared to the alloy with initial lamellar microstructure of 3054 kJ/mol, the alloy with initial equiaxed microstructure had an activation energy of 4155 kJ/mol. As the temperature rises, the rate of corrosion tends to increase. The results suggested that the alloy with initial equiaxed microstructure presented the superior corrosion resistance than the alloy with the initial lamellar microstructure. Additionally, the corrosion morphologies after polarization of the alloy were characterized. And the results show that the surfaces of titanium alloys with initial lamellar microstructure display a comparatively greater incidence of pitting corrosion upon assessment of the corrosion morphology.