Electrochemical characteristics of intermetallic phases in aluminum alloys - An experimental survey and discussion

This paper presents a survey of corrosion potentials, pitting potentials, and electrochemical characteristics for intermetallic particles commonly present in high-strength aluminum-based alloys. Results from relevant pure metals and solid solutions are also presented. It is seen that corrosion potentials and pitting potentials vary over a wide range for various intermetallics. Elaboration of the results reveals that the electrochemical behavior of intermetallics is more detailed than the simple noble or active classification based upon corrosion potential or estimated from the intermetallic composition. Intermetallics capable of sustaining the largest cathodic current densities are not necessarily those with the most noble E-corr, similarly those with the least noble Ecorr will not necessarily sustain the largest anodic currents. The data herein was collected via the use of a microcapillary electrochemical cell facilitating electrode investigations upon intermetallic particles in the micrometer-squared range. This survey may be used as a tool for clarification of localized corrosion phenomena in Al alloys. (c) 2005 The Electrochemical Society. All rights reserved.