Pitting corrosion of bulk glass-forming zirconium-based alloys

The polarization behavior of glassy Zr59Ti3Cu20Al10Ni8 alloy samples was investigated in 1N H2SO4 solution to understand their passivation characteristics in strongly acidic environment. Pitting corrosion tests were performed in acidic chloride medium of IN H2SO4 containing 0.01-0.2N NaCl. Electrochemical investigations were carried out by potentiodynamic and potentiostatic anodic polarization methods at room temperature. The corroded sample surfaces were examined using scanning electron microscopy, and the alloying element distribution across the pits was analyzed using energy dispersive X-ray analysis. The passive films developed at potentiostatic anodic polarization were examined using Auger electron spectroscopy (AES). The results of the present investigation revealed (i) corrosion resistance of Zr-based amorphous alloys is very high in acidic medium and moderate in acidic chloride medium (ii) structural defects and clustered zones of alloying elements deteriorate the corrosion resistance, and (ii) copper plays a significant role in enriching below the passive film and affecting the corrosion behavior. In conclusion, a localized corrosion mechanism is proposed. (C) 2004 Elsevier B.V. All rights reserved.