Abstract:

Hot corrosion has been extensively observed in various high temperature applications, which might cause large economic losses. To deepen the insight and understanding of hot corrosion, herein, we provide a detailed discussion on hot corrosion induced by molten sulfate salt, in which Na₂SO₄ is the main chemical reactant. The hot corrosion is triggered and sustained by the negative solubility gradient of protective oxide from the oxide/salt interface to salt/gas interface. In this work, we reviewed several key factors, including temperature, gas composition, molten salt composition, alloy element and external stress, influencing the hot corrosion of alloy beneath the molten salt. The application of anti-corrosion coating seems to be the most effective and commercial mothed to mitigate hot corrosion. Therefore, the progress of the development of effective coatings, e.g., Ni-Cr coatings, aluminide coatings, silicide coatings and MCrAlY(X) coatings, has also been summarized.

Key words: Hot corrosion, Molten sulfate salts, Protective oxide layer, Dissolution, Anti-corrosion coatings