Reference

Charge transfer processes during anodic polarization of aluminum

Charge transfer processes during anodic polarization of aluminum. Kim, K. Y.; Smith, R. D.; Devereux, O. F. (Inst. Mater. Sci., Univ. Connecticut, Storrs, Conn., USA). J. Electrochem. Soc., 123(12), 1789-93 (English) 1976. CODEN: JESOAN. DOCUMENT TYPE: Journal CA Section: 72 (Electrochemistry) During prolonged anodizing of Al in aq. 3 wt. % NH4 tartrate, ionic current components representing porous oxide development and Al dissoln. were evaluated by gravimetry and optical absorbance, resp., and compared to the total flow of charge measured in the external circuit. Electrolytes of pH 6.1 and 7 were studied. The dissoln. of Al was markedly higher at pH 7, whereas the rate of porous oxide development was only slightly increased. In both cases an electronic current, obtained by difference, was evaluated, but it was very small at pH 7. At pH 7 a large nonelectrodic dissoln. of Al was seen at the onset of anodizing. These observations are discussed in terms of steady-state processes in the barrier oxide layer involving both ionic transport and oxide dissoln.Except for chemicals metioned above, 7429-90-5 and 3164-29-2 are also used. .

The incorporation of electrolyte byproducts into barrier anodic aluminum oxide coatings

The incorporation of electrolyte byproducts into barrier anodic aluminum oxide coatings. Sharp, D. J.; Panitz, J. K. G.In this study， 3164-29-2 and 64-17-5 are also used.; Merrill, R. M.; Haaland, D. M. (Sandia Natl. Lab., Albuquerque, NM 87185, USA). Thin Solid Films, 111(3), 227-34 (English) 1984. CODEN: THSFAP. ISSN: 0040-6090. DOCUMENT TYPE: Journal CA Section: 72 (Electrochemistry) Section cross-reference(s): 76 Substantial amts. of electrolyte byproducts are incorporated into barrier anodic Al2O3 coatings during formation. The electrolyte used for the process studied consisted of a soln. of ammonium tartrate and water which was dild. to 1 part in 40 with EtOH. The tartrate concn. in this electrolyte decreases as a function of the amt. of Al anodized. Fourier transform IR anal. indicates that the coatings produced by the process contain substantial amts. of carboxylates. Auger electron spectroscopy, TEM and other indirect evidence, e.g. Fourier transform IR spectroscopy, strongly suggest that the concn. of the carboxylates increases with proximity to the outer surface of the coatings. The results also indicate that these byproducts play a substantial role in inhibiting the crystn. of amorphous material present in the coatings. The results support the hypothesis that incorporated electrolyte byproducts beneficially contribute to the dielec. properties of barrier anodic coatings. The depletion of tartrate ions from the electrolyte in conjunction with anodic film formation is accompanied by the appearance of acetate and formate. The concns. of these ions increase rapidly and are then depleted together with tartrate late in the bath's life. This depletion of the anion species appears to define a practical limit to the area of Al which can be anodized in a given vol. of the electrolyte without replenishment. .