Corrosion Behavior of Mo5Si3-Based Metal Silicide Alloy

The Mo5Si3-based alloy consisting of small particles Mo3Si uniformly distributed in a Mo5Si3 matrix was fabricated by hot press sintering method. Corrosion properties of the alloy were investigated using anodic polarization and immersion tests in 1 mol/L HCl, 1 mol/L H2SO4 and 1 mol/L NaOH solutions, respectively. Results showed that the alloy had very low corrosion rate in three tests solutions due to the formation of a stable and compact passive film (SiOx, MoO3 and MoO2) as well as the chemical stability and strong bonds with large covalent component inherent to Mo5Si3-based alloy. Only a slight pitting could be observed on the sample surface as a result of selective corrosion of the Mo3Si phases with respect to the Mo5Si3 matrix in NaOH solution. Meanwhile, the alloy exhibited excellent electrochemical corrosion resistance in acidic environments excluding NaOH solution. The alloy was less corrosion resistance because of the formation and dissolution of Na2SiO3 and damaging the integrity of SiO2 preservative in NaOH solution.