Publication: Hot corrosion behaviour of slurry aluminide coating in molten alkali salts
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Date
2022-08-16
Authors
Mohamed Jawhar, Mohammad Taufiq
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Abstract
Material durability is important in high-temperature applications such as Thermal Energy Storage (TES) and Biomass Superheater Boiler Tubes. One of the challenges that materials used in TES and Biomass Superheater Boiler Tubes are constant contact with corrosive molten salt at high temperatures. This project aims to develop an aluminide coating on 304 stainless steel substrates by using the slurry aluminizing coating technique and to evaluate the corrosion behaviour of aluminide coating in various molten salt compositions. In this study, the uncoated 304 stainless steel and aluminide-coated 304 stainless steel were subjected to corrosion tests in 2 types of molten salts (95.5 wt.% KCl + 4.5 wt.% NaCl and 60 wt.% NaNO3 + 40 wt.% KNO3) for 100 h at 700°C. After completion of the corrosion test, the weight loss and corrosion test for each sample were determined. The Al-coated 304 stainless steel shows a better corrosion resistance in molten salts 2 by the formation of FeNi, Al3Fe2Ni9, and Al2O3 phases with 0.4334 mm/y of corrosion rate value. Next, the raw (uncoated) 304 stainless steel shows the lowest corrosion resistance in molten salt 1 by the formation of FeNi, Cr0.6Fe1.4NiO4, Fe2NiO4, and Fe2O3 phases with 3.4123 mm/y of corrosion rate value. Thus, the aluminide-coating produced by using the slurry aluminizing technique was able to protect the substrate metal layer from
corrosion attack.