Exploratory corrosion tests on alloys in molten salts at 900 °C

Coyle, R.T.; Thomas, T. M.; Lai, G.Y.

doi:10.1007/bf02833573

Cited by 27 publications

(22 citation statements)

References 4 publications

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“…Nextgeneration solar power conversion systems in CSP applications are targeting high-temperature, advanced fluids to operate in the range of 600-800°C, which are temperatures that exceed the range of nitrate stability. Chloride molten salts are promising candidates, but are corrosive to common alloys used in vessels, heat exchangers, and piping at these elevated temperatures [4]. Containment material degradation is a major concern to meet commercial viability of next generation CSP plants [5].…”

Section: Introductionmentioning

confidence: 99%

Corrosion of alloys in a chloride molten salt (NaCl-LiCl) for solar thermal technologies

Vidal

Tirawat

2016

Solar Energy Materials and Solar Cells

169

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a b s t r a c tNext-generation solar power conversion systems in concentrating solar power (CSP) applications require high-temperature advanced fluids in the range of 600-800°C. Current commercial CSP plants use molten nitrate salt mixtures as the heat transfer fluid and the thermal energy storage (TES) media while operating with multiple hours of energy capacity and at temperatures lower than 565°C. At higher temperatures, the nitrates cannot be used because they decompose. Molten chloride salts are candidates for CSP applications because of their high decomposition temperatures and good thermal properties; but they can be corrosive to common alloys used in vessels, heat exchangers, and piping at these elevated temperatures. In this article, we present the results of the corrosion evaluations of several alloys in eutectic 34.42 wt% NaCl -65.58 wt% LiCl at 650-700°C in nitrogen atmosphere. Electrochemical evaluations were performed using open-circuit potential followed by a potentiodynamic polarization sweep. Corrosion rates were determined using Tafel slopes and Faraday's law. A temperature increase of as little as 50°C more than doubled the corrosion rate of AISI stainless steel 310 and Incoloy 800H compared to the initial 650°C test. These alloys exhibited localized corrosion. Inconel 625 was the most corrosionresistant alloy with a corrosion rate of 2.80 7 0.38 mm/year. For TES applications, corrosion rates with magnitudes of a few millimeters per year are not acceptable because of economic considerations. Additionally, localized corrosion (intergranular or pitting) can be catastrophic. Thus, corrosion-mitigation approaches are required for advanced CSP plants to be commercially viable.

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Section: Introductionmentioning

confidence: 99%

Corrosion of alloys in a chloride molten salt (NaCl-LiCl) for solar thermal technologies

Vidal

Tirawat

2016

Solar Energy Materials and Solar Cells

169

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“…Introduction of oxygen and moisture have deleterious effects as discussed earlier. Studies will be discussed contrasting additions of oxygen [15,16], wet and dry O2 streams [20,21], and use of chlorine in situ above the salt [17].…”

Section: Ullage Gas Effects On System and Chemistrymentioning

confidence: 99%

“…The influence of moisture results in a twofold effect: introduction of oxygen for worsening corrosion and evolving HCl, which will act to exacerbate corrosion in the head space. During experiments with chloride salts, an observed continually evolved fuming was observed causing further corrosion of metal near the crucible where tests took place [21]. The partial pressure of water during tests was estimated to be 0.1-1% and half of alloys tested disintegrated after six days of exposure under these conditions (900°C, NaClMgCl 2 ) [21].…”

Section: Ullage Gas Effects On System and Chemistrymentioning

confidence: 99%

“…During experiments with chloride salts, an observed continually evolved fuming was observed causing further corrosion of metal near the crucible where tests took place [21]. The partial pressure of water during tests was estimated to be 0.1-1% and half of alloys tested disintegrated after six days of exposure under these conditions (900°C, NaClMgCl 2 ) [21]. Experiments were performed investigating corrosion of alloys and ceramics exposed to a molten chloride with a Cl 2 -Ar sparge, which simulated conditions used for a reconversion of CaO to CaCl 2 necessary in a pyrochemcial process for plutonium recovery.…”

Section: Ullage Gas Effects On System and Chemistrymentioning

confidence: 99%

“…Further literature reviews of moisture in CO 2 environments did indicate that small amounts of moisture, even at the ppm levels [39]. Corrosion tests at 900°C for carbonates, chlorides and hydroxide salts qualitatively indicate that moisture is less of an issue of relative importance as compared to chloride salts, however this would need to be investigated further [21].…”

Section: Ullage Gas Effects (Atmosphere Anode Gases Cathode Gases)mentioning

confidence: 99%

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Corrosion mechanisms in chloride and carbonate salts.

Kruizenga¹

2012

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State of the art thermal solar power uses nitrate salts as the heat transfer fluid. In order to increase operating efficiencies high turbine inlet temperatures must be achieved. Different heat transfer fluids must be considered for this purpose. Corrosion mechanisms in chloride and carbonate based salts were reviewed to better understand the practical implications for using either salt in a solar system.

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Preparation and Thermophysical Properties of High Thermal Conductive Solar Salt/MWCNTs Composite Materials

Wang

et al. 2019

ChemistrySelect

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To improve the heat transfer performance of the photothermal molten salt (Solar salt), a composite material of Solar salt doped with MWCNTs (Multi‐walled carbon nanotubes) which has excellent thermal conductivity, was prepared and analyzed. XRD was used to analyze the composition of the composite, which remained as NaNO3 and KNO3 without change. XPS was used to analyze the C1s energy spectrum, the carbon nanotubes were purified and the impurity groups were greatly reduced after high temperature melting. Melting point, phase change enthalpy and specific heat of composite materials were measured by DSC; the decomposition temperature of composite material were measured by TGA; the density was measured by the Archimedes method; the thermal diffusivity was measured by the laser flash method. The thermal conductivity was calculated according to the thermal conductivity formula: k=Cp⋅ρ⋅α. When the Solar salt was doped with 0.4% MWCNTs, the thermal conductivity was greatly improved, increasing by 87% to 0.77 W/(m⋅k). And the influence of carbon nanotubes on the spatial structure of nitrate was analyzed by Raman spectroscopy. This composite material had superior thermal properties than Solar salt and was expected to be applied in solar thermal power generation to improve solar energy utilization efficiency.

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Exploratory corrosion tests on alloys in molten salts at 900 °C

Cited by 27 publications

References 4 publications

Corrosion of alloys in a chloride molten salt (NaCl-LiCl) for solar thermal technologies

Corrosion of alloys in a chloride molten salt (NaCl-LiCl) for solar thermal technologies

Corrosion mechanisms in chloride and carbonate salts.

Preparation and Thermophysical Properties of High Thermal Conductive Solar Salt/MWCNTs Composite Materials

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