Abstract: PS45 coating was prepared on 20 steel substrate by high velocity oxygen fuel spray deposition. The sealing agent was prepared with TEOS as the sealing agent base material and Cr₂O₃, Al₂O₃, ZrO₂, CeO₂ as fillers. Then, the sealing agent was used to seal the pores existing in the PS45 coating.The hot corrosion behavior of the PS45 coating with and without sealant was studied by coating a film of mixed salts 75%Na₂SO₄+25%NaCl(mass fraction) on sample surface and corrosion at 750 ℃. The composition, structure and morphologies of the corrosion products were investigated by XRD, SEM and EDS.The results show that the mass gain is obvious in the corrosion process for PS45 coating.The corrosion products on the sample surface are identified as Cr₂O₃, NiCr₂O₄ and NiO. However, the mass gain of PS45 sealant coating is about half of the mass gain of unsealant coating. The corrosion products of the cristobalite and layered CeO₂ on the sample surface have a certain blocking effect for molten salt corrosion during the corrosion process. The Cr-rich oxide layer formed at interface of the sealing layer and PS45 coating can furtherly improve the corrosion resistance of the sealing layer.