HIGH CORROSION-RESISTANCE OF AMORPHOUS FE-CR-P ALLOYS

Amorphous iron-base alloys typically contain large amounts of metalloids (B,P,C). The role of the metalloids is to facilitate the glass-formation but they very strongly influence the corrosion behaviour, too. Addition of phosphorus to iron-chromium alloys modifies the passivation mechanism and leads to self-passivation even in strongly acidic deaerated solutions. A highly stable chromium oxyhydroxide passive film with significant amounts of oxidized phosphorus incorporated is formed on the surface of the P-containing alloy. The amorphous alloy Fe-10Cr-13P-7C shows an extremely high resistance against localized attack in Cl- -containing solutions. This is due to a low pit initiation rate and a high repassivation ability of the P-containing alloy.