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Title: Protective coatings for alloys in contact with molten drawsalt (NaNO/sub 3/-KNO/sub 3/)

Molten drawsalt (NaNO/sub 3/-KNO/sub 3/) is being considered as the energy transfer and storage medium for many solar central receiver applications. In an effort to reduce the cost of the containment material while maintaining corrosion resistance, alloys with aluminide coatings have been examined while in contact with molten drawsalt for more than 6000 hours at 600/sup 0/C. The alloys examined were 2-1/4 Cr-1 Mo, 5 Cr-1/2 Mo, and 9 Cr-1 Mo low-alloy steels, and 316 stainless steel. The results show a steady, albeit slow, net weight loss over the course of the experiment. The weight loss has been attributed to spalling of Al/sub 2/O/sub 3/ from the surface (the occurrence of Al/sub 2/O/sub 3/ is a result of the aluminizing process) and dissolution of corrosion products NaAlO/sub 2/ and/or NaFeO/sub 2/ during post-immersion handling. Scanning electron micrographs of exposed surfaces revealed little or no corrosion of the base metal. It has been concluded that aluminide coated alloys could provide significant cost savings (approx. 50%) relative to Incoloy 800, and provide at least equivalent corrosion resistance.
Authors:
; ;
Publication Date:
OSTI Identifier:
6741849
Report Number(s):
SAND-82-8028
ON: DE83002505
DOE Contract Number:
AC04-76DP00789
Resource Type:
Technical Report
Research Org:
Sandia National Labs., Livermore, CA (USA)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; CHROMIUM-MOLYBDENUM STEELS; CORROSION PROTECTION; PROTECTIVE COATINGS; MOLTEN SALTS; CORROSIVE EFFECTS; POTASSIUM NITRATES; SODIUM NITRATES; STAINLESS STEEL-316; TOWER FOCUS COLLECTORS; ALUMINIUM OXIDES; CORROSION PRODUCTS; EXPERIMENTAL DATA; HEAT STORAGE; HEAT TRANSFER FLUIDS; MATERIALS TESTING; PHASE DIAGRAMS; WEIGHT; ALKALI METAL COMPOUNDS; ALLOYS; ALUMINIUM COMPOUNDS; CHALCOGENIDES; CHROMIUM ALLOYS; CHROMIUM STEELS; CHROMIUM-NICKEL STEELS; COATINGS; CONCENTRATING COLLECTORS; CORROSION RESISTANT ALLOYS; DATA; DIAGRAMS; ENERGY STORAGE; EQUIPMENT; FLUIDS; HEAT RESISTANT MATERIALS; HEAT RESISTING ALLOYS; INFORMATION; IRON ALLOYS; IRON BASE ALLOYS; MATERIALS; MOLYBDENUM ALLOYS; NICKEL ALLOYS; NITRATES; NITROGEN COMPOUNDS; NUMERICAL DATA; OXIDES; OXYGEN COMPOUNDS; POTASSIUM COMPOUNDS; SALTS; SODIUM COMPOUNDS; SOLAR COLLECTORS; SOLAR EQUIPMENT; STAINLESS STEELS; STEELS; STORAGE; TESTING 140702* -- Solar Thermal Power Systems-- Central Receiver; 360105 -- Metals & Alloys-- Corrosion & Erosion