Corrosion behavior of HDA (hot-dip aluminized) carbon steel C45 half immersed in molten salts (NaCl, Na ₂ SO ₄ ) isothermally at 973 K

AbstractAluminized carbon steel C45 samples of 0.44 wt.% carbon content were immersed half in a molten salt mixture (NaCl + Na2SO4 with a ratio of 1:3) at a temperature of around 973 K over three different exposure periods: 8, 24, and 72 h. It was observed that a new intermetallic layer (emergent layer) formed at the interface between the steel substrate and the pre-formed intermetallic layers as a result of further outward and inward diffusion of Al, Fe, and C, as indicated by a metallographic study involving SEM combined with EDS spot analysis and elemental analysis. It was also observed that flake-like new phases precipitated in both halves, largely composed of Fe–Al–C–O elementary components, where presumably, the steel C45's high carbon content and the prolonged exposure to high temperatures contributed to further chemical reactions between the elements of HDA specimens and the molten salts’ aggressive Cl and S elements. Moreover, they accelerated the rate of oxidation/corrosion of the hot-dip aluminized C45 steel specimens at high temperatures. Gibbs free energies calculations of some of the corrosion products confirmed the composition of the oxide scale detected experimentally.Keywords: Carbon steel C45molten saltshigh-temperature corrosionhot-dip aluminizing AcknowledgmentsThe authors are thankful to the organizers of the second international conference and exhibition on corrosion and surface protection of steel (CASP 2022), held in Istanbul, Turkey, on 25–26 May 2022, and for providing the opportunity to present a part of this study. The authors would also like to thank all colleagues who contributed to the finalization of this research.Disclosure statementNo potential conflict of interest was reported by the author(s).Data availability statementThe corresponding author can provide experimental data supporting this study.