Aluminium 100uF 25V Electrolytic Polar Capacitor is general-purpose and filter capacitor. Aluminium 100uF 25V Electrolytic Polar Capacitor, whose anode electrode (+) is made of a pure aluminium foil with an etched surface. The aluminium forms a very thin insulating layer of aluminium oxide by anodization that acts as the dielectric of the capacitor. A non-solid electrolyte covers the rough surface of the oxide layer, serving in principle as the second electrode (cathode) (-) of the capacitor. A second aluminium foil called “cathode foil” contacts the electrolyte and serves as the electrical connection to the negative terminal of the capacitor.