Abstract
To identify the role of β‐phase 
precipitates in pitting of heterogeneous Al‐Ta alloys exposed to aqueous solutions, the 
compound was synthesized in bulk form for study by conventional electrochemical and surface analytical techniques. Under conditions of anodic polarization in chloride‐free buffer solutions of various pH, 
is passive, however the phase is capable of supporting electron transfer reactions like anodic 
evolution and cathodic 
evolution at enhanced rates compared to pure Al. Correspondingly, 
is effectively noble with respect to its microstructural surroundings. Facile electron transfer appears to be traceable to the fact that the surface oxide is relatively thin and contains a high fraction (∼0.4) of 
which has a low electronic resistivity. Since reduction reactions occur at enhanced rates, 
precipitates are expected to act as local cathodes under free corrosion conditions in aggressive environments. Surface analysis shows that significant Ta enrichment of an air‐formed oxide film occurs upon initial exposure to solution. Subsequent anodic polarization up to the 
evolution potential does not induce further enrichment however.