Structure and composition of anodic films formed on binary Mg-Al alloys in KOH-aluminate solutions under continuous sparking

Anodizing of binary Mg-Al alloys (2-12% at Al) and intermetallic Mg17Al12 was studied in a solution containing 3 M KOH 0.6 M KF + 0.21 M Na3PO4, with and without addition of 0.4 M and 1.1 M aluminate. The anodic films were formed under continuous breakdown and anodizing was accompanied by intensive sparking and oxygen evolution. The films formed on Mg-Al alloys in a bath containing 1.1 M aluminate were composed of MgAl2O4 spinel and that on intermetallic Mg17Al2 Of gamma -Al2O3 and MgAl2O4. (C) 2001 Elsevier Science Ltd. All rights reserved.