Hot corrosion behavior of thermal sprayed using HVAF and DS techniques with Tribaloy-400 coatings for solar energy storage container

The present study investigates the high-temperature corrosion behaviour of Tribaloy-400 (T-400) coatings deposited on ASTM A516 steel using two thermal spray techniques: (i) High Velocity Air Fuel (HVAF) spraying and (ii) Detonation Spraying (DS). The coated specimens were exposed to a molten solar salt environment consisting of 60% NaNO 3 –40% KNO 3 at 500 °C for exposure durations up to 1000 hours to evaluate their oxidation and corrosion resistance. Phase analysis indicated the formation of stable protective oxide phases, including Cr 2 O 3 , Co 3 O 4 , and CoMoO 4 , in both coating systems. Elemental mapping revealed that the HVAF coating retained a uniform Cr–Mo–Si–O enriched surface with minimal molten salt penetration even after prolonged exposure of 1000 hours. In contrast, the DS coating exhibited comparatively deeper salt ingress into the coating microstructure, which contributed to increased degradation and spallation. SEM observations showed that the HVAF coatings possessed a dense and well-bonded microstructure, along with the formation of thermodynamically stable oxides such as Cr 2 O 3 , CoCr 2 O 4 , and CoMoO 4 , resulting in superior resistance to molten salt-induced corrosion. However, the relatively porous nature of the DS coating promoted salt-assisted oxide dissolution, leading to higher mass gain, increased spallation, and accelerated degradation during extended exposure. Comparative evaluation of both coating techniques was carried out to identify a suitable coating process and feedstock combination for high-temperature CSP applications.