Study on AC Etching of Aluminum in Hydrochloric Acid Solution by Cyclic Chronopotentiometry

The AC etching of aluminum foil (99.99%) in 5% hydrochloric acid solution was studied by cyclic chronopotentiometry, SEM observation and electrostatic capacity measurement. Prolonged cyclic chronopotentiograms at a frequency of 50Hz were measured under different current densities and temperatures, and expressed in three-dimensional graphics as a function of cycle number. Potentialcycle number curves were also derived from the chronopotentiograms at arbitrary times. Change in the peak potential at anodic half cycles was closely related to the potential in the subsequent cathodic half cycles. The time, tp, at which the anodic peak is attained and the value of the anodic peak potential, Ep, varied with cycle number. The potential -cycle number curve was greatly affected by the current density at the cathodic half cycles and changes in tp and Ep became greater as the electrolyte temperature was increased. When the etching was carried out with a high anodic peak potential and without large fluctuation in the potential-cycle number curve, the pits were densely formed on the aluminum foil, providing high electrostatic capacity.