CORRELATION BETWEEN THE THICKNESS AND THE SPECIFIC MASS OF AN ANODIZATION LAYER ON ALUMINUM AND THE MEASURED CURRENT TRANSIENT

For anodizing of aluminium in a sulphuric acid (15 mass%) solution at constant voltage, the current initially jumps to a high value and decr eases rapidly to a low value in the first few seconds; thereafter the current rises to a constant level. The course of the current versus ti me is common for all applied voltages and temperatures. However, the h igher the voltage and temperature are, the faster and higher the rise and constant level will be. The shape of this current-time curve is re presentative for the specific anodization layer. Exponential relations has been found for the different characteristic points (minimum, maxi mum and steady-state current and the corresponding times) of the curre nt density-time curve versus voltage and temperature. Also for the thi ckness and the apparent specific mass of the oxide layer, exponential functions versus voltage and temperature were found. In this work it h as been proved that a correlation exists between the measured steady-s tate current density, the thickness and the apparent specific mass of the layer. For the formed oxide layers the measured mean real specific mass value is the same as that one which has already been published.