Obtaining white anodic aluminum oxide (AAO) is a major challenge in the surface finishing industry. The present work presents a cost-effective route to design light-scattering morphologies through submicrometric hollows homogeneously dispersed in the depth of the oxide layer, created by localized hydrogen evolution. To this end, cathodic steps are added in alternance with anodic steps in a bipolar pulse anodizing process performed in 2 M sulfuric acid. The mechanisms of nucleation and growth of the targeted hollows within the AAO are highlighted by combining in situ electrochemical measurements and high magnification SEM observations. The aesthetic performances in terms of white color, evaluated by reflectance spectroscopy in comparison with a white reference, are directly related to the size, shape and distribution of the hollows, controlled by both the parameters of the cathodic step and the thickness of the unit anodic oxide layers.
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