Development of Superhydrophilic 6061 Aluminum Alloy by Stepwise Anodization According to Pore-Widening Time

Abstract

This study created alumina structures with the highest hydrophilic properties on 6061 aluminum alloy. The anodization process was applied to make various aluminum oxide structures. To create uniform alumina structures on top of a 6061 aluminum alloy surface, after conducting the first anodization in 0.3 M oxalic acid at 40 V at 0 <sup>o</sup>C, the alumina was removed using a mixture of chromic acid and phosphoric acid. Then, secondary and tertiary anodization was performed using the same electrolyte conditions as the primary anodization for 30 minutes at 40 V, respectively. Pore-widening (PW) of oxide film formed after the secondary anodic oxidation was performed for 20, 30, and 40 minutes in 0.1 M phosphoric acid solution. The PW time control allowed various oxide structures to be created, and reduced the area of the outermost surface in contact with water droplets. The smaller the initial area of water droplets, the better the hydrophilic phenomenon. The surface area can be represented as a solid fractional value. Surfaces with solid fraction values of less than or equal to 0.5 were superhydrophilic. This well-controlled anodization process with a pore-widening step can be used to create excellent superhydrophilicity on various metallic substrates, expanding their usefulness and efficacy.