Highly corrosion-resistant amorphous CrNiP alloys

Abstract

To prepare highly corrosion-resistant amorphous CrNiP alloys, the amorphizable composition range was determined and the corrosion resistance was assessed from the weight loss in concentrated HCl and HF solutions. All the amorphous CrNiP alloys showed extremely high corrosion resistance in both concentrated HCl and HF solutions. The effects of crystallinity and the chromium content on the corrosion resistance were clearly observed in the concentrated HCl solution. In the concentrated HF solution, all the CrNiP alloys were extremely corrosion resistant, while the binary CrNi alloys had low corrosion resistance. The amorphous CrNi19P alloys also exhibited the low corrosion rate of about 0.004 mm per year in the mixture of aggressive 12 M HCl and 47% HF solution. The effects of crystallinity and alloying with phosphorus and chromium on the corrosion resistance in HCl and HF solutions were explained in terms of the homogeneity of alloys, the formation of an elemental phosphorus layer during the initial dissolution, and the formation of the highly protective, passive chromium oxyhydroxide.