Use of unconventional organic acids as anodization electrolytes for fabrication of porous alumina

The possible occurrence of porous anodic oxide films on aluminium in aqueous solutions of lactic, propionic, glycolic and succinic acid has been investigated. The anodizations have been carried out in galvanostatic conditions at different current densities, with fixed acid concentration, external bath temperature and process duration. Lactic and propionic acids resulted in patterning of the aluminium substrate, whereas glycolic and succinic acids showed formation of a corrugated oxide layer. The morphology of the outer oxide layers was similar in feature spacing for both acids, and independent on the anodization conditions. Inspection of the inner side confirmed the porous nature of the glycolic acid oxide. The pore cell size measured for glycolic acid oxide increased with increasing current density, from ~125 to ~300 nm. The highest porous layer growth rate obtained was ~0.5 ¿m/min.