HIGH RESISTANCE ANODIC OXIDE FILMS ON ALUMINIUM

Abstract

The thicknesses of oxide films formed in aqueous borate solutions were obtained by the spectrophotometric method after developing the interference colors by evaporating a very thin film of gold or bismuth onto the oxide. The refractive index of the stripped films was determined by the Becke immersion method as 1.57 to 1.58 at 5 900 Å wavelength. The dielectric constant was estimated as 9.8 ± 0.5. Experimental data on the steady state ionic current density, I, through the oxide as a function of the field strength, E, in the oxide could be represented by I = I₀ exp −(W − qaE)/kT where I₀ = 2.24 × 10⁷ A cm⁻², W = 1.3 ± 0.15 eV, q = 3e, a = 2.95 ± 0.15 Å.