The Role of Native Oxides on the Corrosion Mechanism of Laves Phases in Mg–Al–Ca Composites

Abstract

Magnesium–aluminum–calcium composites are characterized by thermally stable Laves phases, which enable high-temperature material applications. Nevertheless, immersing the material into an electrolyte causes an increased corrosion rate as a consequence of micro-galvanic effects among the Laves phases and the matrix. The Volta-potential difference determined under atmospheric conditions on a freshly polished surface using Scanning Kelvin Probe Force Microscopy (SKPFM) is a valid measure for the micro-galvanic coupling and the dynamic growth kinetics of a native oxide film. In the present study, the time-dependent native oxide film formation of magnesium–aluminum–calcium alloys is analyzed via in situ SKPFM measurements. An inhomogeneous evolution of the Volta-potential on the Laves phases compared to the matrix indicates heterogeneous native oxide formation.