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 α-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.