Investigating localized corrosion susceptibility arising from Sc containing intermetallic Al3Sc in high strength Al-alloys

Low-level scandium additions to Al lead to the formation of Al3Sc dispersoids, which have a significant effect on grain refinement during thermomechanical processing. Electrochemical measurements have been carried out using a micro-electrochemical capillary cell in order to characterize any influence Al3Sc particles may have on the initiation and propagation of pitting corrosion in aluminum alloys exposed to dilute chloride solutions. On the basis of these measurements, Al3Sc is found to be spontaneously passive with a low self-dissolution rate. It is slightly cathodic to the alpha-Al matrix of Al-alloys in which it would be present, however, cathodic reaction kinetics are sluggish compared to other dispersoid intermetallic compounds. As a result, Al3Sc displays good electrochemical compatibility with Al-alloys and should be expected to pose no greater a corrosion risk than that associated with other dispersoids common in Al alloys; namely Al6Mn, Al3Zr and Al3Ti. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.