Corrosion evaluation of alloys and MCrAlX coatings in molten carbonates for thermal solar applications

Abstract

3 at temperatures higher than 600°C were evaluated using an open-circuit potential followed by a potentiodynamic polarization sweep to determine the corrosion rates. Because the best-performing alloys at 750°C were In800H followed by SS310, these two alloys were selected as the substrate material for the MCrAlX coatings. The coatings were able to mitigate corrosion in molten carbonates environments. The corrosion of substrates SS310 and In800H was reduced from ~2,500 µm/year to 34 µm/year when coated with high-velocity oxyfuel (HVOF) NiCoCrAlHfSiY and pre-oxidized (air, 900°C, 24 h, 0.5°C/min) before molten carbonate exposure at 700°C in bone-dry CO 2 atmosphere. Metallographic characterization of the corroded surfaces showed that the formation of a uniform alumina scale during the pre-oxidation seems to protect the alloy from the molten carbonate attack.

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

“…Similar results were obtained in pre-oxidized alumina-forming alloys exposed to molten eutectic MgCl 2 -KCl at 700°C in a flowing Ar atmosphere. 4,5,8 Qualitative adhesion tests of the best-performing coating over 310SS and In800H after oxidation were performed using standard ASTM 3359. A diamond saw was used to cut through the coating, creating a grid with 2-3-mm spacing.…”

“…We are investigating corrosion in molten salts at high temperatures for solar applications and its mitigation to obtain degradation of containment materials around 20 µm/yr or lower, thus providing a lifetime for CSP plants of 30 years or more. [3][4][5][6][7][8][9] Corrosion behavior of steel containers in latent TES molten eutectic KCl-LiCl from 310 to 420°C in air and argon has been evaluated with the long-term weight-loss technique for up to 4000 h of immersion. The effect of water and other impurities in the salt were also studied, with pitting corrosion detected and the addition of 2 wt% H 2 O causing a severe increase in corrosion in these environments.…”

Microstructural characterization and evolution under high temperature oxidation of CoCrAlYTa-10%Al2O3 coating deposited by high-velocity oxygen fuel thermal spraying

“…During thermal spraying process, molten or semimolten droplets impacted on the substrate and rapidly cooled to form a laminar coating composed of many layers where the pores mostly existed [8]. The added Al 2 O 3 particles were normally drawn into the pores of the coating, resulting in a lower porosity of the as-sprayed coating [19]. Figure 3(b) shows that white fine particles uniformly dispersed in the coating and many main gray phases with a shape of oval are observed from the microstructure.…”

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.…”