Biblioteca Digital

Passivity in aqueous solutions is reviewed and several proposed passivity models are outlined. Passivity in the non-aqueous solution of acetic acid-acetic anhydride was observed and characterized by voltage measurements. These measurements show a striking similarity to those in aqueous solution. This suggests that the same basic process is involved in both cases. Sulfuric acid, nitric acid, and chromium trioxide were used as passivating agents in the non-aqueous medium and their order is the same as in aqueous solution. The difference in the actual species in solution raises the question of the applicability of several of the passivity models outlined. Finally, suggestions are made for experiments to clarify the passivation process using nonaqueous passivated specimens.