EFFECTS OF ALLOYING ELEMENTS ON THE ELECTROCHEMICAL CHARACTERISTICS OF IRON ALUMINIDES

Effects of alloying elements on the electrochemical characteristics of iron aluminides in the H2SO4, H2SO4 + KSCN and HCl solutions were inv estigated using electrochemical tests. The corrosion morphologies in i ron aluminides were analysed by utilising optical microscopy. It was f ound that the addition of Cr and Mo to iron aluminides increased the c orrosion potential, pitting potential and repassivation potential. The active current density, passive current density and reactivation curr ent density decreased as Cr and Mo were added. In the case of Mo addit ion, the passive current density was slightly higher in the H2SO4 solu tion than in solutions containing SCN- and Cl-. When B was added to sa mples, the corrosion potential and repassivation potential decreased, whereas the active current density, passive current density, reactivat ion current density and pitting potential increased. Iron aluminides c ontaining Mo and Or showed remarkably improved intergranular and pitti ng corrosion resistance to SCN- and Cl- solution. On the other hand, B addition accelerated granular and intergranular corrosion by precipit ation of borides.