| Effects of Cr, Mo and Boron additions on the pitting corrosion of iron aluminides(Fe-28at%Al alloy) in the solution containing Cl were investigated using electrochemical tests. The corrosion morphologies were examined by utilizing the optical microscope and scanning electron microscope(SEM). It was observed that the addition of Cr and Mo to Fe-28at%Al increased corrosion potential, pitting potential and repassivation potential. The active current density and passive current density decreased as Cr and Mo were added. In the case of Mo addition, the passive current density was slightly higher in H₂SO, solution than in solutions containing Cl. When boron was added to Fe-28at%Al, corrosion potential and repassivation potential decreased, whereas the critical anodic current density, passive current density, and pitting potential increased, Fe-28at%Al containing Mo and Cr showed remarkably improved pitting resistance against Cl attact, due to the formation of chromium oxide(Cr₂O₃) and molybdenum oxide(MoO₃) and to the enrichment of molybdate(MoO₄^(2-)) on the surface. In the case of Fe-28at%Al containing boron, pits were found at grain boundaries which boride precipitates have aluady existed. |
|
