Mechanism of Corrosion Tunnelling With Special Reference to Cu3Au

Abstract

Abstract A flat corrosion interface is unstable on alloys undergoing preferential dissolution of one component. This instability results from the uneven accumulation of the less soluble component which enables pits to develop and grow into corrosion tunnels. Electron microscope observations of CU3AU exposed to a ferric chloride solution suggest that surface diffusion or ionization and re-deposition of gold occurs on the walls of corrosion tunnels and that this accounts for the discrepancy between observed and calculated tunnel diameters. No evidence was found to support the volume diffusion theory of tunnel formation.