The corrosion behavior of Ni-Ta-5P alloys in concentrated hydrochloric acid

The addition of 30 at% or more tantalum to Ni-5P alloy greatly enhances the corrosion resistance in 12 M HC1 at 30°G The corrosion rate of amorphous Ni-40Ta-5P alloy is about three orders of magnitude lower than that of Ni-5P alloy. The addition of sufficient amounts of tantalum to Ni-SP alloys leads to an ennoblement of the open circuit potential and to spontaneous passivation. The addition of a large amount of tantalum to the Ni-Ta alloy contained a small amount of phosphorus, such as 5 at%, enhances the formation of the tantalum enriched passive film which prevents oxidation of phosphorus.