Corrosion Behavior of Oxide-Covered Cu47Ti34Zr11Ni8 (vitreloy 101) in Chloride-Containing Solutions

The corrosion resistance of oxides that form in air on Vitreloy 101 (Cu47Ti34Zr11Ni8) metallic glass ribbons in NaCl and HCI solutions was studied by scanning electron microscopy, X-ray photoelectron spectroscopy and potentiodynamic polarization. The air-exposed alloy was covered by a TiO2/ZrO2 layer overlying a Cuenriched region beneath. Ni was absent at the surface. Segregation of Ti and Zr was driven by exothermic oxide formation. Immersion in NaCI or HCI caused pitting corrosion by local Galvanic reactions that depleted less noble Ti, Zr and Ni from the pit interiors, leaving them rich in more noble Cu. Corrosion products containing Ti and Zr accumulated around the pit. Pits were most numerous in 1.0 M HCI due to TiO2(s)/Ti3+(aq) equilibrium that resulted in rapid solubilization of the oxide, creating local weaknesses and an increased rate of pit formation. On average, Ti preferentially dissolved from the oxide in accord with metal nobility arguments. (C) 2014 Elsevier B.V. All rights reserved.