Fe-Si系合金の不働態化特性について

Abstract

With the object of determining the relationship between passivation behavior of Fe-Si alloys and silica formation on the alloy surfaces, anodic polarizations were conducted in IN H2SO4 for iron, 6 and 14% Si-Fe alloys, and pure silicon.At about -0.2V (vs. S.H.E.), the anodic polarization curves of 6 and 14% Si-Fe alloys began to deviate from that of iron, resulting from silica formation on the alloy surfaces. Silica was not accumulated on the surface of 6% Si-Fe alloy, which scarcely hindered anodic dissolution of the alloy.The silica formation and its removal from the surface were alternately repeated during anodic dissolution, and after the end of removal, a fresh surface was exposed.The above phenomenon in the transition stage from active to passive state probably caused the prolongation of current oscillation on noble side and the delay of passivation. The silica accumulation on the surface of 14% Si-Fe alloy remarkably reduced the anodic dissolution of the alloy in active and passive states. Fayalite (Fe2SiO4) was also anodically polarized in 1N H2SO4 However, no evidence was shown that fayalite immediately controlled the passivation phenomenon of Fe-Si alloys.