Superheated Steam Of Zirconium Alloys Containing Small Amounts Of Iron and Copper or Nickel

Alloys of zirconium containing small amounts of iron and copper or nickel have corrosion resistance in superheated steam superior to that of the Zircaloys. At 540 C (1004 F) and 600 psi lowest rates are about 4 mdd (2.4 mpy) and at 650 C (1202 F) and 600 psi rates are about 6.8 mdd (4.1 mpy). High initial rates lead to an extrapolated intercept of about 4 mg/sq cm at 650 C (1202 F). The thickening films are subject to cracking at sharp radii. Absorption of corrosion product hydrogen decreases markedly as exposure temperature is raised from 540 to 650 C (1004 to 1202 F). This phenomenon is not understood. Metal embrittlement due to oxygen absorption becomes an increasingly serious problem as temperature is raised. Corrosion rate at 650 C (1202 F) is not affected by flow rate (300 ft/sec) or by presence of oxygen or oxygenhydrogen mixtures in the steam.