Hot Corrosion of T22, T23, and T91 Steels in Na2SO4 Salts at 800 and 900 ℃

Ferritic T22, T23, and T91 steels were corroded in Na2SO4 salt at 800 and 900 ℃, and their hot corrosion behavior was studied. The corrosion resistance increased in the order of T22, T23, and T91. The good corrosion resistance of T91 at 800 ℃ was mainly attributed to Cr, which led to the formation of thin scales. By contrast, the amount of Cr in T22 and T23 was not enough to form protective scales so that thick, porous, bi-layered scales formed on T22 and T23 at 800 ℃. Nonetheless, T22, T23, and T91 suffered rapid scaling and dissolution of scales into the salt at 900 ℃. Iron oxides were the major corrosion products in this study.