High-temperature corrosion of aluminized-American Iron and Steel Institute (AISI) 1020 steel with sodium chloride (NaCl) and sodium sulphate ( $${\hbox {Na}}_{2} {\hbox {SO}}_{4}$$ ) deposits was studied using isothermal oxidization in a dry air environment at $$700{^{\circ }}\hbox {C}$$ for 49 h. NaCl and $${\hbox {Na}}_{2} {\hbox {SO}}_{4}$$ deposits on the aluminide layer interfered with protective alumina/aluminium oxide ( $${\hbox {Al}}_{2} {\hbox {O}}_{3}$$ ) scale formation on the steel substrate. Chlorine and sulphur gases ( $${\hbox {Cl}}_{\mathrm{2g}}$$ and $${\hbox {S}}_{\mathrm{g}}$$ , respectively) released into the atmosphere corroded the protective $${\hbox {Al}}_{2}{\hbox {O}}_{3}$$ layer. Corrosion of the $${\hbox {Al}}_{2}{\hbox {O}}_{3}$$ layer was also due to local formation of iron oxide ( $${\hbox {Fe}}_{2}{\hbox {O}}_{3}$$ ). $${\hbox {Fe}}_{2}{\hbox {O}}_{3}$$ growth is attributed to ferric chloride ( $${\hbox {FeCl}}_{3}$$ ) vaporization. $${\hbox {S}}_{\mathrm{g}}$$ diffusion into the $${\hbox {Al}}_{2} {\hbox {O}}_{3}$$ scale via $${\hbox {Al}}^{3+}$$ vacancy defects led to the formation of aluminium sulphide on the aluminide layer surface. Cl and S consequently induced hot corrosion of the aluminized steel, thereby increasing cyclic oxychloridation and sulphidation rates at high temperatures.