Aluminium electrolytic condenser

The electrolytic condenser is formed by the immersion of aluminium in a suitable electrolyte, a thin film of oxide functioning as the dielectric. The physical properties of the film, such as its porosity, thickness, and electrical conductivity, vary in different cases. It is on the formation of badly conducting films at the surface of a metal anode, permitting the maintenance of high voltages between the electrolyte and the anode, and preventing the passage of ions (leakage current), and upon the relative stability of the film when formed, that commercial application is possible [see also Abstract 1929B01570]. The film is rapidly formed when the correct polarity is applied, hence by a suitable arrangement of electrodes rectification is possible. Although this valve action has been observed with most metals under suitable conditions, only two, aluminium and tantulum, have gained wide use commercially.