Whitening of aluminum surface by anodizing at high current density in sulfuric acid solution

DOI Web Site 22 References
  • Hariyama Tomo
    R&D Center, Chemicals Business General Headquarters, Nihon Kagaku Sangyo Co., Ltd
  • Ito Kazunobu
    Marketing Department, Chemicals Business General Headquarters, Nihon Kagaku Sangyo Co., Ltd
  • Saito Teruyoshi
    Marketing Department, Chemicals Business General Headquarters, Nihon Kagaku Sangyo Co., Ltd
  • Watanabe Sumitaka
    R&D Center, Chemicals Business General Headquarters, Nihon Kagaku Sangyo Co., Ltd
  • Ono Sachiko
    School of Advanced Engineering, Kogakuin University

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Other Title
  • 硫酸中での高電流密度の陽極酸化によるアルミニウム表面の白色化

Abstract

<p>In this study, we examined a method for whitening of aluminum surface by anodizing in sulfuric acid solution, with the aim of industrializing the process. Anodic oxidation in sulfuric acid solution at 2.5 Adm‒2 for 120 s achieved whitening of the aluminum surface, but localized burning occurred. When anodizing was performed at low current density after anodizing at higher current density for short time (2.5 Adm‒2 for 4.5 s), white anodic film was successfully obtained without burning. Cross-sectional SEM (scanning electron microscopy) observation of white film revealed that the etching by pretreatment created an uneven surface, and the pore branching created an uneven metal- oxide interface. The fluctuating value of the film thickness obtained by length measurement using SEM were 0.2-0.3μm. This value is sufficient to whiten the anodic film due to increase of diffusion reflection at the film surface and the metal-oxide interface. These results indicate that the difference in peak voltage between the first and second anodizing resulted in the formation of a branched pore structure and the achievement of film whitening.</p>

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