Corrosion of Alloy 800H in caustic-contaminated superheated steam at 538/sup 0/C (1000/sup 0/F)

Technical Report · Tue May 01 04:00:00 EDT 1979

DOI:https://doi.org/10.2172/6169410· OSTI ID:6169410

Griess, J. C.; Maxwell, W. A.

Alloy 800H has very high corrosion resistance to high-temperature steam and is a promising material for superheater tubes in high-temperature gas-cooled reactors. The material, however, is susceptible to stress-corrosion cracking in some caustic environments. Experience at fossil fired power plants has shown that excursions in the sodium concentration of the boiler feed water brought about by load changes can result in sodium concentrations of 20 to 30 ppB in the steam for short times. Consequently, we conducted this experimental program to determine if sodium dissolved in steam at this level adversely affects corrosion of Alloy 800H. The corrosion resistance of four heats of Alloy 800H was determined in superheated steam containing 20 to 30 ppB Na as sodium hydroxide at 538/sup 0/C (1000/sup 0/F). Two of the heats contained the specified minimum carbon content (0.05%), and two contained near the maximum (0.10%). The test was conducted in a once-through loop at an operating power plant and used plant steam into which a dilute solution of sodium hydroxide was injected. Specimens stressed to 90% of the ASME design yield stress showed no signs of stress-corrosion cracking or other forms of localized attack during a 3991-h test. All four heats of the alloy corroded at 6.1 ..mu..m/year (0.24 mil/year), which though higher than in pure stream was still low.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 6169410
• Report Number(s): ORNL/TM-6797
• Country of Publication: United States
• Language: English

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