Local Burning Phenomena in Sulfuric Acid Anodizing: Analysis of Porous Anodic Alumina Layers on AA1050

Abstract

The development of local burning phenomena during galvanostatic anodizing of the AA1050 aluminum alloy in a sulfuric acid electrolyte was analyzed. The oxide hillocks formed during burning were controlled and characterized at different anodizing times. Field-emission-scanning electron microscope images, electron probe microanalysis, energy-dispersive X-ray spectroscopy analysis, and microhardness measurements showed that the porous anodic alumina (PAA) that formed the hillocks had a different structure, composition, and mechanical behavior than the standard PAA. Moreover, Fe and Si were detected at the very top parts of the hillocks, suggesting a connection between intermetallic particles and burning initiation.