Transient Response of the System Al/Al₂O₃/Electrolyte. Part I. Galvanostatic Transients

Abstract

Voltage transients under galvanostatic conditions are investigated for the system AI/Al,O,/electrolyte (glycol-borate) and the results, along with similar results obtained by Dewald for the system Ta/Ta,O,/ electrolyte (0.1 N H'SO,), are analyzed according to the dielectric relaxation model due to Dignam. This model accounts for the general form of the transients, but systematic discrepancies are apparent. Modification of the model to include two independent ion-current-driven dielectric relaxation processes gives essentially exact agreement with the data and values for the constants in accord with those obtained earlier from potentiostatic transient measurements.--Nous etudions les transitions de voltage sous des conditions galvanostatiques pour le systeme AI/AI,O,/ electrolyte (glycol-borate) et nous analysons les resultats, de mime que les resultats similaires obtenus par Dewald pour le systeme Ta/TaZO,/electrolyte (0

Simulation of the electrical transient during the porous anodizing of pure aluminium substrate

“…The relation used to fit the second part of the voltage transients in the 20 to 1000 A/m 2 range, is based on the previous works of Goad and Dignam [6] and Wu and Hebert [9,10]: V(t) = V ss + (V 0 -V ss ).exp(-λ 2 .t) (t m ≤ t < ∞) (4) with V 0 = S 0 .t m and λ 2 is a constant for a fixed value of the current density, under the considered anodizing conditions. Figure 5 provides an example of the experimental transient obtained at 300 A/m 2 compared with the corresponding fitting curve (λ 2 = 0.35s -1 , V ss = 85.8V and V 0 = 1284.1V).…”

“…From this point of view, despite previous preliminary works [6][7][8][9][10], further efforts are necessary to explain the initial electrical transients obtained either under galvanostatic anodizing mode or in potentiostatic anodizing conditions, as well as to correlate simultaneously these electrical transients with the surface nanoporosity of the aluminium substrates.…”

Anodic Oxide Growth on Tantalum with AC + DC Fields: I . Experimental Procedures and Results

“…To reproduce the experimental observation s that the initial rise of current density at constant field for films annealed in boiling water to reduce the latent ionic conductivity to a low value is given by dJ/dt ~ j2 [2] and that the current density eventually settles at the steady-state vMue for the constant field, one may write dS/dt =BJ(fE -S) [3] Equation 3 defines a relaxation-type process with a singletime T = 1/BJ. In the steady state, dS/dt = 0 giving S = fE so that the steady-state current density is given by…”

“…Ideally, we wished to apply a field E(t) = Eo + Ele ~t (real part) [1] where Eo and E1 are constants, and measure an ionic current density Jio,~ = Jo + Jle j~ [2] where Jo is the dc ionic current density and Y~ is the (complex) amplitude of the ionic current density. The required admittivity is defined as the (complex) quantity J~/E~.…”

The roles of the surface oxide film and metal-oxide interfacial defects in corrosion initiation on aluminum

“….1 Decay of the excess field, E -E2, with charge passed (= fj, Idt ) during galvanostatic transients performed on the system AI/AI2O3 in the glycol borate electrolyte [97]. Where Ei and E2 are the initial and final steady-state field strengths, I is the current density, t is time 11 x plots for the film on the EP 4min (@25 V @ 5 °C) foils (with dielectric relaxation) 56…”