Characterizing the microstructure and mechanical and electrochemical properties of novel ceramic/polymer sandwich structural coatings

In this study, a polymer bond layer was incorporated between the chemically bonded composite sol–gel coating (CB-CSG) and stainless steel substrate to form sandwich structure coatings for improving the coating's corrosion resistance in aqueous solutions. The low processing temperatures of CB-CSG coatings and a specified high temperature polymer (siloxane) make it possible to prepare polymer/CB-CSG composite coatings with an unusual combination of mechanical properties and corrosion resistance. Compared with non-polymer CB-CSG coatings, the ceramic/polymer sandwich coatings exhibit lower hardness and elastic modulus due to the infiltration of polymer into the CB-CSG ceramic coatings. However, the polymer layer of the sandwich structure coatings may remarkably reduce the residual stress in the coatings. Electrochemical characterization and salt spray tests indicate that the polymer layer is very efficient for improving the overall corrosion resistance.