Effect of Aluminum Sulfate in the Sulfuric Acid Electrolyte on Anodic Polarization

Abstract

Anode polarization measurements have been made over a wide range of concentration of the electrolyte. For each concentration of acid, the coating ratio (weight of coating divided by weight of aluminum reacting) was also determined. Aluminum sulfate dissolved in the electrolyte decreased the polarization value, but was only about 1/5 as effective as free . The presence of aluminum sulfate in the electrolyte had little effect on the coating ratio. Additions of oxalic, glycolic, and tartaric acids had only a small effect on the polarization, but increased the coating ratio and decreased the rate of solution of the oxide coating in the electrolyte in which the coating was formed.