The state of metal surfaces after blasting treatment Part I: Technical aluminium

Abstract

Abstract The aluminium–magnesium alloy EN‐AW 5754 is studied with SEM, energy‐dispersive x‐ray imaging (EDX), AES and XPS after treatment by chemical etching and blasting with glass beads or alumina grit. Blasting proves to change more than the surface profile. The freshly treated surfaces are fully covered with a carbon contamination of characteristic oxygen content ‘etch ≪ glass ≪ grit’ and average thickness ‘grit ≪ glass ≪ etch < 10 nm’. Beneath the carbon, an oxide mix is found as a continuous layer on the Al matrix. The oxide Na 2 O is transferred from both blast materials whereas CaO is observed after glass bead treatment only. Etching almost removes Mg but blasting retains traces of MgO. On the etched surface, the oxide layer (average thickness: glass ≪ etch ≪ grit < 10 nm) is Al 2 O 3 . Just after blasting with glass or alumina Al 2 O 2.9 and Al 2 O 1.3 , respectively, are detected. After glass blasting, these Al atoms continue to oxidize whereas the incomplete Al oxide is almost stable after alumina blasting. These findings show that blasting produces particular chemical states that rule the interaction between the aluminium alloy and another material such as a coating or adhesive. Copyright © 2002 John Wiley & Sons, Ltd.