Effect of inorganic silicate sealing treatment on corrosion behaviour for HVAF sprayed Fe-based amorphous coatings

Sealing treatment is an effective, environmentally friendly, and economical coating surface modification technology. To clarify the inorganic silicate sealing mechanism and concentration dependence on corrosion behaviour, HVAF-sprayed Fe-based amorphous metallic coatings (AMCs) were sealed by Na2SiO3 solution with various concentrations, and their microstructure, electrochemical performance, and surface chemistry were characterised in detail. The results showed that Na2SiO3, in the form of a silicon-oxygen bond (Si-O), could effectively bond with the coating surface inside the pore defects. In addition, the optimal concentration was proved to be 1 mol/L, and the corresponding passivation current density could be reduced to (2.38 ± 0.33) × 10−6 A/cm2, which was an order of magnitude lower than that of as-sprayed coating. This was due to the incomplete filling of the sealant at lower concentrations and the release of water vapour at higher concentrations. This work aims to provide guidance for the practical application of silicate sealing treatment.