Aluminum electrolytic capacitors are made of two aluminum foils and a paper soaked in electrolyte. The anode aluminum foil is anodized to form a very thin oxide layer on one side and the unanodized aluminum acts as cathode; the anode and cathode are separated by paper soaked in electrolyte, as shown in Fig. 8.10A and B.
If an aluminum electrolytic capacitor has a reverse voltage applied, its capacitance will decrease, its leakage current will increase and the capacitor may explode. Besides the application of a reverse voltage, overvoltage, AC voltage or capacitor failure, internal gas pressure can be generated at a rate the package cannot contain mechanically.
Aluminum electrolytic capacitors, often called electrolytic capacitors, are usually selected because they offer a relatively large capacitance for a relatively small physical size. Aluminum electrolytic capacitors tend to be readily available, and with high voltage values (on the order of 700 V).
This oxide layer has a voltage proof of approximately 1 to 1.5 V. Therefore, aluminum electrolytic capacitors with non-solid electrolyte can continuously withstand a very small reverse voltage and, for example, can be measured with an AC voltage of about 0.5 V, as specified in relevant standards. [citation needed]
In non-polar aluminum electrolytic capacitors and motor-start aluminum electrolyte capacitors a second anode foil substitutes for the cathode foil to achieve a non-polar capacitor in a single case. These figures show typical constructions of the non-surface-mount aluminum electrolytic capacitors.
Aluminum electrolytic capacitors with non-solid electrolytes have an exceptional position among electronic components because they work with an electrolyte as liquid ingredient. The liquid electrolyte determines the time-dependent behavior of electrolytic capacitors. They age over time as the electrolyte evaporates.