Ultra-fast fabrication of porous alumina film with excellent wear and corrosion resistance via hard anodizing in etidronic acid

Abstract This paper describes a fast-fabrication strategy for hard-anodized film prepared on 6063T5 aluminum alloy in environmentally friendly etidronic acid (HEDP). The mild HEDP anodizing was first investigated at a temperature range of 15–45 °C, just under the burning current densities. The voltage curves and microstructures of the anodized film prepared in HEDP (Eti-film) indicate that 35 °C is the most appropriate temperature for the fast fabrication of Eti-film, in contrast to the micro-arc oxidation (MAO) coating and the seriously surface-corroded Eti-film prepared at 15 and 45 °C, respectively. Then, the HEDP hard anodizing without burning was successfully conducted via a gradient-increase-current approach, resulting in a high growth rate (~ 2.1 μm/min), low porosity (