Plating on anodized aluminum—I. The mechanism of charge transfer across the barrier-layer oxide film on 1100 aluminum
✍ Scribed by J. Gruberger; E. Gileadi
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 1014 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0013-4686
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✦ Synopsis
The mechanism of plating on anodized aluminum was investigated . Porous anodic films were formed on 1100 aluminum and the electrochemical behaviour of a number of test reactions (Ag*/As, Cur'/C,4[Fe(CN) 6 ]° /[Fe(CN)6]3 -and QH 2 /Qwas determined . Hydrogen evolution can damage the oxide film and enhance the rare of electrochemical reactions on the surface . It is not a prerequisite, however, for metal deposition and other electrode reactions. Under the experimental conditions studied, the activity of the pores was not uniform and metal was plated in only a fraction of the pores, even when the total charge passed exceeded that required to fill all the pores tenfold or more . Metal ions can penetrate the barrier layer at the bottom of the pores by migration or diffusion, to be discharged at the aluminum surface . The barrier layer may also act as a heavily doped semiconductor which allows passage of charges with no specificity for the reversible potential of the redox couple tested. Observation of the uniformity of deposition of metals into the pores at an early stage by SEM with electron microanalysis can serve as a powerful tool in determining the best conditions for uniformly filling the pores . This should lead to improvements in the quality of plating on anodized aluminum .