High-temperature corrosion of aluminized-AISI 1020 steel with NaCl and $${\hbox {Na}}₂{\hbox {SO}}₄$$ deposits

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.