Electrochemical kinetic study on the growth of porous anodic oxide films on aluminium

 
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Electrochemical kinetic study on the growth of porous anodic oxide films on aluminium (EN)

Patermarakis, G (EN)
Moussoutzanis, K (EN)

N/A (EN)

Aluminium specimens were anodized galvanostatically in a thermostated and vigorously stirred bath of H2SO4 15% w/v at different bath temperatures and current densities and for long anodization times, sufficient to produce the maximum or near maximum limiting film thickness, and the anodic potential was followed. Results confirmed that the rate controlling step of the steady-state growth of the barrier layer is the charge transport across this layer, which is near solely due to the migration of anions; oxide is produced only in a region adjacent to the Al-Al2O3 interface. Taking into consideration the structural features of the barrier layer oxide and by assuming a uniform oxide nature and one kind of migrating anions or cations, it has become possible to formulate simplified high field ion migration electrochemical kinetic equations. They were found to be non-satisfactory when applied at low anodization temperatures, but become applicable at high temperatures or low barrier layer thicknesses. Their application postulated that the charge transfer at the Al-Al2O3 interface, Al-3e → Al3+, takes place rather through successive ""one electron"" transfer elementary steps. Also, the charge transport across the barrier layer oxide bulk takes place through a concomitant migration of the ions O2-, OH- and SO42- . A model for the ions transport was suggested which gives a physical meaning to the field assisted oxide dissolution at pore bases, explains the incorporation of SO42-, SO3, OH- and H2O and predicts the change of their concentration, of the oxide nature and of the values of kinetic parameters across the barrier layer; it also predicts that an H+ migration may take place during oxide growth. © 1995. (EN)

journalArticle

OXIDATION (EN)
MECHANISM (EN)
HYDROTHERMAL TREATMENT (EN)
anodizing (EN)
PASSIVE FILMS (EN)
porous (EN)
PORE CLOSURE (EN)
TRANSPORT NUMBERS (EN)
AL METAL (EN)
HYDRATION (EN)
OXYGEN (EN)
oxide (EN)
AL2O3 FILMS (EN)
aluminium (EN)
electrochemical kinetics (EN)
growth (EN)

Εθνικό Μετσόβιο Πολυτεχνείο (EL)
National Technical University of Athens (EN)

Electrochimica Acta (EN)

1995


PERGAMON-ELSEVIER SCIENCE LTD (EN)



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