التفاصيل البيبلوغرافية
| العنوان: |
Corrosion resistance of MCrAlX coatings in a molten chloride for thermal storage in concentrating solar power applications. |
| المؤلفون: |
Gomez-Vidal, Judith C. |
| المصدر: |
NPJ Materials Degradation; 12/1/2017, Vol. 1 Issue 1, pN.PAG-N.PAG, 1p |
| مصطلحات موضوعية: |
CORROSION resistance, METAL coating, STAINLESS steel, SOLAR power plants, HEAT storage |
| مستخلص: |
Corrosion evaluations of Incoloy 800 H (In800H) and stainless steel AISI 310 (310SS), in bare and coated conditions, were performed in 34.42 wt% NaCl – 55.47 wt% KCl at 700 °C in a nitrogen atmosphere. This NaCl–KCl composition has a melting point of 657 °C, which makes it suitable for latent-heat thermal energy storage in concentrating solar power applications. Several nickel-based MCrAlX coatings were tested, where M = Ni and/or Co and X = Y, Ta, Hf, and/or Si. Electrochemical testing was carried out to determine corrosion rates. The bare In800H and 310SS alloys corroded rapidly (~2500 and 4500 µm/yr, respectively, assuming uniform corrosion). Concentrating solar power plants need containment materials with a lifetime of at least 30 years; thus, these corrosion rates are excessive. Corrosion mitigation approaches are being investigated to obtain degradation on the order of 20 µm/yr or lower. The lowest corrosion rate of 190 µm/yr was obtained for atmospheric plasma spray NiCoCrAlY coatings pre-oxidized in air at 900 °C for 24 h with a heating/cooling rate of 0.5 °C/min. Metallographic characterization of the corroded surfaces showed that the formation of a uniform thin alumina scale before exposure to the molten chloride system considerably reduced the corrosion of the alloy. However, the rates of corrosion determined herein are considerable, highlighting the relevance of testing materials durability in solar power applications. Solar power: alloys wear protective coats Spraying materials used in solar thermal power stations with protective coatings could minimize corrosion and extend their lifetimes. Chloride salts are stable at temperatures above 600 °C and make excellent candidates for fluids that can deliver heat energy captured from the sun to turbines that generate electricity. Unfortunately, these molten salts are prone to corroding the alloys from which power plant components are typically made. Judith Gomez-Vidal at the National Renewable Energy Laboratory in the US found that spraying and oxidizing NiCoCrAlYTa coatings on inexpensive alloys caused evenly-spread thin alumina films to form, protecting them from corrosion upon exposure to high-temperature salts. Electrochemical measurements revealed that the thicknesses of the coated alloys decreased at rates of 190 microns per year, ever closer to the 20 micron per year rate desired for a 30 year lifespan. [ABSTRACT FROM AUTHOR] |
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