Anodic film on lead-arsenic alloy in sulphuric acid medium

The phase composition, anodic behaviour and semiconducting properties of the anodic film on Pb-6 at.% As alloy have been investigated. The linear relationship between I and t exp 1/2 , where I is the anodizing current density and t the anodizing time, shows that the anodic film growth is controlled by a diffusion mechanism. The experimental results show that the anodic film contains t-PbO, PbOmultPbSO sub 4 , 3PbOmultPbSO sub 4 and some As compounds. The dielectric constant of the film is 2.8x10 exp 2 obtained from the capitance-time relationship measured at 2500 Hz. The Mott-Schottky plot shows that the film is an n-type semiconductor. The flat-band potential is -0.56 V vs. Hg/Hg sub 2 SO sub 4 and the donor density is 7.2x10 exp 15 cm exp -3 for the film obtained at 0.9 V vs. Hg/Hg sub 2 SO sub 4 on a Pb-6 at.% As electrode.