Localized Corrosion and its Inhibition by CO sub 2 of Aluminum and Al-0.5% Cu in Dilute HF Solutions

We have investigated the localized corrosion of sputter-deposited aluminum and Al-0.5% Cu thin film metallizations in dilute HF solutions and the inhibition of this corrosion by CO sub 2 bubbled through the solution. Using electrochemical, optical, and electron analytical techniques, we found in these solutions that: (1) micropitting of aluminum and the alloy occurs at the open circuit potential, which is well negative of the breakdown potential; (2) Al sub 2 Cu precipitates in the alloy markedly increase the pit density and the rate of pit growth by catalyzing the cathodic reaction; and (3) saturating the solution with CO sub 2 inhibits pitting by passivating defects in the oxide film, particularly at Al sub 2 Cu precipitate sites, and by producing a more homogeneous oxide film over the surface.