The Study On Corrosion Property Of Zr-based Bulk Amorphous Alloys And Its Crystalline States

Zr-based bulk amorphous alloys Zr60Al15Ni25, Zr52.5Al10Ni10Cu15Be12.5 and Zr65Al10Ni10Cu15 were prepared by copper suction casting. Crystalline alloys were obtained by isothermal annealing according to its DSC. Through measuring the polarization curves , combination of SEM and EDS,research the corrosion behavior of bulk amorphous alloys and its crystalline states. The different mechanisms between them were discussed.By comparing the corrosion resistance of different components of the bulk amorphous alloys in 0.5mol/L H2SO4 solution, found that alloys all have a very excellent corrosion resistance in the solution and the surface maintained a good states. Only Zr60Al15Ni25 bulk amorphous alloy no significant corrosion, the other two kinds of bulk amorphous alloys have undergone significant corrosion in 2mol/LNaOH solution, but there was no pitting phenomenon. In 3.5 % NaCl solution, alloys occurred significant pitting corrosion and formatted a large number of pit. Because there was a large potential difference between the added alloy elements Cu,Be and other elements,easy to form micro-cell corrosion and reducing the corrosion resistance of Zr60Al15Ni25 bulk amorphous alloy. The corrosion resistance of the same component bulk amorphous alloy in the 3.5% NaCl solution,2mol/LNaOH solution and 0.5mol/LH2SO4 solution corrosion were expressed as the strength of 0.5mol/LH2SO4>2mol/LNaOH >3.5%NaCl.Comparison of the corrosion behavior of bulk amorphous alloys and its crystallization alloys respectively in 3.5% NaCl, 2mol/LNaOH and 0.5mol/L H2SO4, found that a large number of structural weaknesses were occurred in alloys due to structural changes, the corrosion resistance of the annealing crystallization amorphous alloys can be worse than the bulk amorphous alloys. Furthermore, since amorphous alloys are metastable thermodynamic structure, compared with annealing alloys, the surface atoms of bulk amorphous alloys have a higher activity in the solutions. Especially in the NaCl solution, they could form more corrosion pits, but the pits of crystallization alloys growth rapid than amorphous alloys, so the destruction of the alloy is more serious. The occurrence of pitting corrosion behavior can be explained by Point Defect Model (PDM).