(Keynote) The Pretreatment of 2000 Series Al Alloy: In Situ Measurement of the Selective Dissolution & Film Formation
Wednesday, October 14, 2015: 14:00
102-A (Phoenix Convention Center)
The surface conditioning of aluminum alloys frequently involves a sequence of alkaline and acid pretreatments. These steps ideally provide a homogeneous surface chemistry prior to subsequent anodization or conversion treatment. However, the electrochemical properties of the intermetallic phases - such as the S-phase (Al2
CuMg) or the θ-phase (Al2
Cu) - are sufficiently different from the matrix that certain alloy components will be enriched on the surface due to selective dissolution and / or redeposition. The aim of this study is to quantitatively measure the selective dissolution processes and characterize the residual films that form during these pretreatment steps.
Fig. 1 Al, Cu, & Mg dissolution rates (expressed as equivalent currents) and the electrochemical potential during the exposure of AA2024 T3 alloy to a 1.2 M NaOH at 60 °C. Intermetallic Cu and Mg rich particles detach from the surface giving rise to the spikes in the Cu and Mg signals.