ETCHING AND PASSIVATION OF ALUMINUM UNDER ALTERNATING CURRENT.INFLUENCE OF TEMPERATURE

ABSTRACT For high purity aluminum foils etched in 1.3N HCl acid under alternating current, the surface porosity and the electrical capacitance strongly depend on the solution temperature and on the etching time. A maximum of capacitance C M is observed for a given frequency value V M which increases with temperature. In the temperature range 50–60°C, the etching yields a maximum of porosity and a minimum of oxide thickness.