Pore development in anodic alumina in sulphuric acid and borax electrolytes
| Autor: | Peter Skeldon, George Thompson, S.J. Garcia-Vergara, H. Habakaki |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Materials science
Anodizing Borax General Chemical Engineering Inorganic chemistry Alloy chemistry.chemical_element General Chemistry Electrolyte engineering.material Tungsten equipment and supplies Barrier layer chemistry.chemical_compound chemistry engineering General Materials Science Dissolution Layer (electronics) |
| Zdroj: | Corrosion Science. 49:3696-3704 |
| ISSN: | 0010-938X |
| DOI: | 10.1016/j.corsci.2007.03.033 |
| Popis: | The formation of porous anodic films on an Al–3.5 at.%W alloy is compared in sulphuric acid and borax electrolytes in order to investigate pore development processes. The findings disclose that for anodizing in sulphuric acid, the pores develop mainly due to the influences of field-induced plasticity of the film and growth stresses; in borax, field-assisted dissolution dominates. The films formed in sulphuric acid are consequently much thicker than the layer of oxidized alloy and tungsten species are retained in the film. In contrast, with borax, the films and oxidized alloy layers are of similar thickness and tungsten species are lost to the electrolyte. Efficiencies of film growth are also significantly different, about 65% in sulphuric acid and about 52% in borax. The retention of tungsten species during anodizing in sulphuric acid is due to the localization of tungsten in the inner regions of the barrier layer and cell walls, with a layer of anodic alumina separating the tungsten-containing regions from the electrolyte. For borax, the tungsten is distributed more uniformly through the film material, enabling loss of tungsten species to the electrolyte from the pore base. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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