THE ELECTROCHEMICAL POLARIZATION OF ZIRCONIUM IN NACL SOLUTIONS
Abstract
Cathodic and anodic polarization curves of Zr in neutral NaCl solution were determined at constant current densities in the range of 3.5 x 10 to the power of -8 to 3.5 x 10 to the power of -3 amp/sq cm. All potentials were steady state. In aerated 0.5 M NaCl, the cathode reaction occurring below the O limiting diffusion current of 2 x 10 to the power of -4 amp/sq cm was the reduction of O to OH. At current densities above the diffusion wave, H was evolved. A change in salt concentration resulted in a slight shift of the diffusion current due to different O solubilities in the different salt concentrations. In deaerated 0.5 M chloride solution, the O diffusion current decreased with a decrease in O concentration. The value for the slope of the Tafel line was 0.12, and the H overvoltage was 0.83 v at 1 ma/sq cm. Another wave occurred at 2 x 10 to the power of -6 amp/sq cm and can best be explained as the reduction of a surface oxide layer on the metal. Anodically, Zr dissolved in 0.5 M NaCl. The dissolution potential, 0.15 v, was constant with a change in current density. Commerical Zr and pure Hf also dissolved under similar conditions. In neutral sulfate solutions, Zr was passive under anodic treatment. At the higher current densities, above 1 x 10 to the power of -3 amp/sq cm, the potential apparently reached a constant value in about 10 min, followed by a sudden increase in potential to 28.5 v. This high potential was a result of an IR drop across a surface of oxide present on the Zr coupon.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1952
- Accession Number
- AD0003616
Entities
People
- Norman Hackerman
- Olin B. Cecil
Organizations
- University of Texas at Austin