Conductance Measurements in Corrosion Studies of Aluminium
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A new method is suggested for studying the rates of dissolution of oxide film on aluminium and its alloys. The method is based on measuring the conductance between two aluminium (or its alloys) electrodes immersed in 3.0 M HC1 solution at 30.0°C. the oxide layer is activated and dissolved, which means an increase in the electric conductance (aluminium oxide is dielectric). The thicker oxide and films of the barrier type will take longer time to activate. It is known that aluminium and its alloys are usually covered with an air borne oxide film. Also the application of alternating current (AC) leads to the formation of anodic films. This newly suggested method based on conductance measurements was utilized for studying the different conditions of formation of the anodic films. This method was also used to control the sealing effect of air borne oxide films. From this study it could be concluded that the AC voltage and time of anodization clearly affect the corrosion resistance of the oxide film in HCl solution. Sealing with boiling distilled water enhances the corrosion resistance of aluminium distinctly while its effect on the Al-Mn alloy is rather insignificant. The suggested conductance method was used to study the effect of some organic inhibitors on the rate of dissolution of the oxide film on the Al and Al-Mn surface.