Effect of Si addition on the electrochemical corrosion and passivation behavior of Fe-Cr-Mo-C-B-Ni-P metallic glasses

Fe-Cr-based metallic glasses (MGs) have attracted extensive attention for industrial applications due to corrosion resistance that is superior to that of their crystalline counterparts. In this work, the effect of Si concentration on the electrochemical corrosion and passivation behavior of Fe43Cr15Mo14C10−xB5Ni3P10Six (x = 0, 2, 4, 6 at.%) MGs in a 3.5 wt% NaCl solution has been investigated by performing potentiodynamic polarization measurements, electrochemical impedance spectroscopy, cathodic polarization, the Mott-Schottky approach, and X-ray photoelectron spectroscopy (XPS). The addition of a small amount of Si (≤4 at.%) is found to have a beneficial effect on improving the thermal stability and corrosion resistance for this Fe-Cr-based MG system. However, higher Si amounts deteriorate the thermal stability due to precipitation of a (Fe, Cr, Mo)23(C,B)6 phase. Also, all electrochemical measurements show that 4 at.% Si is high enough to improve the passivity stability of the system, whereas higher amounts of Si do not significantly improve the corrosion behavior. The improved passivation ability and corrosion resistance of the Si-doped MGs can be attributed to the formation of a dense and stable passive film rich in Si- and Cr-oxides.