| High purity aluminum samples are anodized in 2% oxalic acid solution(21.5∼32℃, 0.1∼2.5amp/d㎡, 11.2∼65 volts) and in sulfuric acid solution (5∼25%, -3∼40℃, 1∼2.5amp/d㎡, 6.3∼23 volts). The experimental results lead to the following conclusions. The relationships between the anodization current i, voltage V and the barrier layer thickness D are well expressed as follows: D=203993V/[4.573T(log i-7.342)+29965] where i, V, D and T are expressed in amp/㎠, volt, Angstrom and absolute degree. Cell sizes increase linearly with anodization voltages whereas pore sizes are almost independent of anodization voltages below 30 volts and increase with anodization voltages above 30 volts. Cell and pore sizes are very little function of anodization temperature and current density, which indirectly affect cell and pore sizes through their contribution to anodization voltages. The porosity decreases rapidly with increasing anodization voltages below 30 volts whereas it changes very little above 30 volts. |
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