The effect of the microalloying of Hf on the corrosion behavior of ZrCuNiAl bulk metallic glass

Bulk metallic glasses of Zr_65-xHf_xCu _17.5Ni₁₀Al_7.5 with Hf = 0 and 1 at.% and bulk metallic glass composite with Hf = 2 at.% were prepared by copper mould casting. The corrosion behavior of the alloys obtained were investigated in 3% NaCl, 1N H₂SO_4, and 1N HCl solutions, respectively, by electrochemical measurements. It is found that all three alloys are spontaneously passivated in 3% NaCl and 1N H₂SO₄ solutions, but exhibit active dissolution in 1N HCl solution. The single amorphous phase of BMG with 1 at.% Hf shows excellent corrosion resistance in 3% NaCl solution due to the structural and chemical homogeneousness of the amorphous phase and to the effect of Hf on promoting the formation of protective film.