Corrosion resistance of MCrAlX coatings in a molten chloride for thermal storage in concentrating solar power applications

Abstract

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.

Corrosion behavior of metallic alloys in molten chloride salts for thermal energy storage in concentrated solar power plants: A review

“…Some methods like adding corrosion inhibitors [40][41][42] in the melts or forming a protective layer on alloys [36,[43][44][45] have been studied to mitigate the corrosion rates of metallic alloys in molten chlorides at high temperatures.…”

“…In the protective layer development for molten chlorides, research focused on 1). Ceramic layers like Al 2 O 3 [36,[43][44][45] and Yttriastabilized zirconia (YSZ) [45], 2). Metallic layers such as nickel based alloy coatings [44][45].…”

Review of supercritical CO2power cycles integrated with CSP

“…Chloride and carbonate salt blends have been proposed and tested, but coming after new challenges . The corrosion mechanisms of candidate salts and corresponding mitigation approaches are still an area of ongoing which are badly needed for component designers . Nickel alloys are decided to be adopted in the receiver and TES, as shown in Table .…”

“…[124][125][126] The corrosion mechanisms of candidate salts and corresponding mitigation approaches are still an area of ongoing which are badly needed for component designers. [127][128][129][130][131] Nickel alloys are decided to be adopted in the receiver and TES, as shown in Table 7. Compared with molten salt, particle as heat carrier is cheaper and more stable at high temperatures.…”

A simple method for the inhibition of the corrosion of carbon steel by molten nitrate salt for thermal storage in concentrating solar power applications

“…In this context, numerous studies have explored the corrosion behaviour of potential construction materials with different storage media or heat transfer fluids. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Molten nitrate salt, known as Solar Salt, is the most technologically mature solution for CSP. It consists of 60 wt% NaNO 3 -40 wt%KNO 3 .…”