STABILITY OF ZIRCONIUM PASSIVE FILMS IN NITRIC AND SULFURIC-ACID-SOLUTIONS

Anodic oxide films were formed galvanostatically on zirconium in nitri c and sulphuric acid solutions. The stability of the formed oxide film s were investigated. The effects of formation voltage, formation curre nt density and frequency on the dissolution behaviour of the formed ox ide layers in both media were studied. Open-circuit potential and impe dance measurements were used. The results reveal that the anodic oxide films formed in nitric acid solutions are more stable than those form ed in sulphuric acid solutions under the same conditions. The stabilit y of the anodic oxide films on zirconium was found to depend on the fo rmation medium rather than the dissolving solution.