Molten Al—Si alloy corrosion resistant composite coating and preparation method and application thereof

A preparation method for the molten Al—Si alloy corrosion resistant composite coating, wherein the composite coating comprises an aluminized layer and a TiO2 film layer from a surface of a substrate to the outside in sequence, the composite coating further comprises an Al2O3 film layer prepared by an atom layer vapor deposition, and the Al2O3 film layer is located between the TiO2 film layer and the aluminized layer, wherein the aluminized layer comprises an Fe(Al) phase diffusion layer, an Fe-Al compound layer and an Al2O3 layer from the substrate to the outside in sequence, wherein comprising the following steps:

• step S1:
• making a surface treatment to an Fe-based alloy, and then aluminizing with a solid powder penetrant;
• step S2:
• sand-blasting the aluminized Fe-based alloy;
• step S3:
• washing and drying the Fe-based alloy which has been sand-blasted;
• and
• step S4:
• depositing the TiO2 film layer on a surface of the dried aluminized Fe-based alloy by using an atom layer vapor deposition.