Abstract:
The local burning phenomenon on the surface of the anodic alumina films is studied under wide range of current densities, anodizing times and anodizing temperature. The growth of nodules occurs at low anodizing temperature (0 0C) and at relatively high current density (10-40 mA/cm2). However, the local burning does not obtain at low current density i.e. 5 even at 0 0C. Moreover nodules formation is not existed on the surface of the anodic alumina films fabricated under the same previous anodizing conditions (5-40 mA/cm2) but at high anodizing temperature (20 0C). In fact, the increment of current density, voltage or electric field increases the local heat. Dissipation of local heat plays big role to prevent local burning rather than reduction of anodizing temperature. Therefore heat transfer is more important than decreased temperature of the electrolyte only which is enhanced the local burning. No obvious effect of anodizing time on occurrence of local burning because of the initial growth of nodules forms at the first seconds of anodizing time. The initial behavior of the voltage-time response and the ∆V/∆t-time transient is a good indicator for nodules growth.
