A silicon-modified aluminide diffusion coating was developed on AISI 304 stainless steel via a powder-based Al–Si process and vacuum heat treatment at 1050 °C. Oxidation behavior was evaluated in air at 1100 °C for 100 h, and hot corrosion performance was investigated electrochemically in a molten Na2SO4–NaCl–V2O5 salt mixture at 750 °C. Uncoated AISI 304 exhibited rapid oxidation kinetics with thick, cracked Fe2O3/ Fe3O4 scales and high mass gain. In contrast, the Al-Si diffusion- coated steel showed an order-of-magnitude lower weight gain, associated with the formation of a dense, continuous Al2O3- rich scale. Electrochemical measurements revealed a 1.5-fold reduction in corrosion current density for the coated sample, indicating suppressed anodic dissolution in the molten salt. The improved performance is attributed primarily to the protective Al2O3 scale; direct evidence of a synergistic role of silicon was not observed. The results demonstrate that Al-Si diffusion coatings offer a cost-effective solution for extending the high-temperature durability of austenitic stainless steels in aggressive molten-salt environments.

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