THE CORROSION BEHAVIOR OF AMORPHOUS AND CRYSTALLINE Ni-10Ta-20P ALLOYS IN 12 M HCl

摘要

The addition of a large amount of phosphorus, such as 20 at%, to arc-melted crystalline and rapidly quenched amorphous Ni-10Ta alloys greatly enhances the corrosion resistance in 12 M HCl at 30℃. The corrosion rate of the rapidly quenched amorphous Ni-10Ta-20P alloy after immersion for 168 h is about one order of magnitude lower than that of the arc-melted crystalline counterpart. The open circuit potentials of both alloys are initially ennobled by accumulation of elemental phosphorus having a high activity for the cathodic oxygen reduction. The open circuit potential is further ennobled by spontaneous passivation. The ennoblement of the open circuit potential of the amorphous alloy is faster than that of the crystalline counterpart, because of faster passivation as a result of the formation of a tantalum-enriched passive film.