Resistance of slurry aluminide coatings on pure nickel under different sulphidizing/Hot corrosion conditions at 700 °C. (15th May 2023)

• Record Type: Journal Article
• Authors: Grégoire, Benjamin; Montero, Xabier; Galetz, Mathias C.; Bonnet, Gilles; Pedraza, Fernando
• Is Part Of: Corrosion science. Volume 216(2023)
• Publication Date: 2023-05-15
• Subjects: A. Aluminium -- A. Molten salts -- C. Oxidation -- C. Sulphidation -- C. Type II hot corrosion -- C. Fluxing mechanisms; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2023.111092
• Languages: English
• ISSNs: 0010-938X

Abstract

Abstract: A water-based slurry aluminide coating was elaborated on high-purity nickel and tested in synthetic air, synthetic air + 0.5 % SO2 /SO3 and synthetic air + 0.5 % SO2 /SO3 with sodium sulphate (Na2 SO4 ) deposit at 700 °C. The developed coating considerably increased the oxidation-sulphidation resistance of nickel in the absence of salt through the formation of thin and adherent alumina scales. In contrast, the presence of sodium sulphate decreased the corrosion resistance. Microstructural investigations indicated that aluminium depletion and the related formation of Ni-rich oxides is mainly responsible for the onset of the corrosion attack following sulphation reaction and fluxing mechanisms. Graphical Abstract: ga1 Highlights: Coating based on β-NiAl increases sulphidation resistance through protective α-Al2 O3 . Coating offers limited protection after the incubation period when in contact with solid Na2 SO4 . Initiation of the attack due to fluxing and synergistic dissolution of NiO and Al2 O3 . Aluminium surface concentration and phase transformation are key factors on the onset of the hot corrosion attack. Microstructural observations confirm the formation of the eutectic Na2 SO4 -NiSO4 in Type II conditions.