The positive electrode of the aluminum electrolytic capacitor, the anode lead electrode and the outer casing are all high-purity aluminum, and the medium of the aluminum electrolytic capacitor is an aluminum oxide film formed on the surface of the positive electrode.
The real negative electrode is the electrolyte, which is equivalent to an electrolytic cell during operation, except that the anodized layer on the surface of the positive electrode has been formed. The electrochemical reaction no longer occurs and the current is theoretically zero.
Due to the presence of impurities in the electrodes and electrolyte, a slight leakage current is caused.
From the phenomenon point of view, the common failure phenomena and failure modes of aluminum electrolytic capacitors are: electrolyte dryness, pressure release device action, short circuit, open circuit (no capacitance), excessive leakage current, etc.