Complex influence of temperature on oxalic acid anodizing of aluminiumстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 сентября 2019 г.
Аннотация:Two-step aluminium anodizing is widely used to prepare oxidefilms with a highly-ordered porousstructure through the whole thickness. It can be realized solely at relatively low values of current densityin the kinetic anodizing regime that makes this process extremely time-consuming. Temperature is animportant thermodynamic parameter which is able to accelerate chemical reactions and mass-transportand, thus, could be suggested as an effective tool to control the growth rate of anodic alumina. Here wereport a systematic study of the porous anodic aluminafilms formation in 0.3 M oxalic acid electrolyte ina wide temperature range. The influence of electrolyte temperature on the kinetics of aluminiumanodizing and on the morphology of the obtained anodic aluminafilms is addressed quantitatively.Current transients registered at various temperatures are used for the calculation of the apparent acti-vation energy of the anodization process in both mild and hard anodizing regimes. In the case of thickoxidefilms and high electrolyte temperature, the increase in diffusion current contribution leads toswitching the kinetically controlled anodizing to the mixed regime which results in destroying thehexagonal pore ordering. Based on the experimentalfindings, rational electrolyte temperatures andporous layer thicknesses for thefirst and second anodizing steps are proposed as a guide for expresspreparation of aluminafilms with well-ordered porous structure.