Molten Salts Induced Hot Corrosion of High Temperature Protective Coatings: Research Progress

High temperature hot corrosion is one of main failure modes for the hot components. The Na2SO4 and NaCl molten salts can accelerate the hot corrosion at high temperatures and even lead to the catastrophic accidents. Thus, this research discussed the molten salts (Na2SO4 or/and NaCl) induced hot corrosion with Na2SO4 as the main corrosion reactant. The corrosion behavior and performance characteristics of two typical types of hot corrosion were introduced. Several hot corrosion models and mechanisms were introduced, as well as the reaction formulas and corrosion mechanisms of Na2SO4, NaCl, and Na2SO4+NaCl molten salts. According to the current research status, the protective coating is an optimal approach in the hot corrosion reduction. The advanced progress of the MCrAlY coatings, NiAl coatings, thermal barrier coatings, and novel coatings was summarized. In addition, the methods to further improve the corrosion resistance of coatings were investigated. Finally, the development direction of protective coatings was predicted.