Author(s): F. Le Coz, L. Arurault & R. S. Bes
Electrical transients were recorded during the anodizing of highly pure
aluminium in phosphoric electrolyte, carried out in potentiostatic mode
(25-150V) or in galvanostatic conditions (20-1000A/m2).
reproductibility is satisfactory, according to the low standard deviations.
For the galvanostatic mode, the voltage experimental transients show a “bell
shape”, characterized by some significant parameters (S0, tm, Vm, Vss).
mathematical relations were then proposed to simulate the voltage transient
curves considering two parts, i.e.
before and after the maximum (Vm, tm).
validity of these computational simulations was next checked by comparison
with the corresponding experimental curves.
All the corresponding fittings of
voltage transients are in good agreement, especially for the first part of the
experimental curves, within the current densities range.
Then, these computational simulations were correlated with the
corresponding experimental FEG-SEM plan-views.
By analogy with the
nucleation phenomena during the metal electrodeposition, the “bell shaped”
curves could be interpreted by the initial formation of a highly resistive oxide
layer, followed by the subsequent appearance of the nanopores.
formation was in part explained showing that the Vm experimental values
obtained with the galvanostatic mode are closed to the previous critical voltage
value Uc initializing the anodic dissolution phenomenon.
electrical transients, anodic film, simulation, nanopores, anodizing.
Anodizing of aluminium and its alloys is an established electrochemical process,
discovered in 1855 by H.
Buff and developed in 1911 by De Saint Martin.
Size: 6,910 kb
Paper DOI: 10.2495/ECOR070161
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