Corrosion performance of molybdenum silicides in acid solutions

The corrosion performance of Mo–22 at.% Si, Mo–24 at.% Si and Mo–25 at.% Si alloys in 0.5 M hydrochloric acid (HCl) and 0.5 M sulfuric acid (H2SO4), at room temperature, has been evaluated using electrochemical techniques. Employed techniques included potentiodynamic polarization curves (PC), linear polarization resistance (LPR) and electrochemical noise in current (ENC). The alloys contained either α-Mo or Mo5Si3 in a Mo3Si matrix. The results show that in almost all cases the three alloys exhibit a passive behavior, and the corrosion resistance increases as follows: Mo–22 at.% Si < Mo–25 at.% Si < Mo–24 at.% Si in both solutions. Also, for each alloy, in all cases there was a selective corrosion of the α-Mo and Mo5Si3 phases with respect to the Mo3Si matrix.