Pitting Corrosion of Amorphous Ni-Zr Alloys in Chloride Ion Containing Sulfuric Acid Solutions
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The pitting corrosion behavior of the melt-spun amorphous Ni–Zr alloys with 30–75 at% zirconium, the crystalline arc-melted counterparts and the sputter-deposited Ni–Zr alloys with 20–84 at% zirconium was examined by electrochemical measurements in deaerated 0.5 kmol/m<SUP>3</SUP> H<SUB>2</SUB>SO<SUB>4</SUB> with and without 0.1 kmol/m<SUP>3</SUP> NaCl at 303 K. In the sulfuric acid solution without Cl<SUP>−</SUP>, these alloys were spontaneously passive and their potentiodynamic behavior was similar to each other. In the Cl<SUP>−</SUP>-containing solution, all the melt-spun amorphous alloys suffered pitting during anodic polarization and the pitting potential decreased with an increase in zirconium content. On the other hand, the crystalline arc-melted low zirconium alloys suffered pitting but no pitting observed for the crystalline alloys containing 70 at% zirconium or more. In addition, the pitting potential increased with the zirconium content of crystalline alloys. All the sputter-deposited alloys did not suffer pitting regardless of the amorphous and crystalline structures. Therefore, the melt-spun amorphous alloys were the most susceptible to pitting corrosion. A marked difference was observed in the pitting behavior between the shiny side (top side) and the dull side (wheel side) surfaces of the melt-spun ribbon. The pits initiated from the dull side surface. Thus, the dull side surface could be responsible for such an unusual pitting behavior of the melt spun ribbon.
- MATERIALS TRANSACTIONS
MATERIALS TRANSACTIONS 38(5), 443-450, 1997-05
The Japan Institute of Metals