Inorganic silicate coatings, as a type of inorganic paint, exhibit the superior long-term anti-corrosion performance, heat resistance, and weather resistance. Compared to the conventional organic coatings, inorganic silicate coatings are more environmentally friendly, aligning with the development of eco-friendly coatings. However, pure inorganic silicate coatings face some issues such as high brittleness, susceptibility to cracking, and poor water resistance, thus restricting their practical application. Extensive research has been conducted on the modification of these coatings to enhance the mechanical properties and anti-corrosion performance of inorganic silicate coatings. It is essential to review the current research on the modification of inorganic silicate coatings to accelerate progress in both research and practical applications in engineering. This review represents the modification of inorganic silicate coatings with various materials affecting the overall performance of the coatings in varying degrees. Based on a spatial multi-scale approach, the relevant modifying materials are categorized into three scales, i.e., macro-scale, meso-scale, and micro-scale.

In the macro-scale, the modifying materials include inorganic substances such as silica sol, aluminum phosphate (AlPO₄), and calcium hydrogen phosphate (CHP), while organic materials consist of organo-silicon emulsions, silane coupling agents, acrylic resins, and epoxy resins. Silica sol significantly enhances the corrosion resistance of coatings via increasing their degree of crosslinking. Phosphate compounds promote the polymerization of silanol groups by providing H⁺ ions, thereby accelerating the curing of the coatings and improving their water resistance. Organic modifiers increase the internal crosslinking density and flexibility of the coatings, while also imparting hydrophobic and self-cleaning properties, by introducing functional groups such as hydroxyl and carboxyl groups into the silicate curing process.

In the meso-scale, the modifications primarily utilize micron-sized fillers, i.e., zinc-type fillers, layered structure fillers, and other metallic and metal oxide fillers. Zinc-type fillers encompass zinc powder, zinc oxide, and zinc silicate. Layered structure fillers include mica powder, two-dimensional transition metal carbides (Ti₃C₂T_x), and layered double hydroxides (LDHs), and other metallic and metal oxide fillers comprise aluminum powder, zinc-aluminum alloy powder, mica iron oxide, titanium (Ti), and titanium oxide (TiO₂). Metal and metal oxide modified fillers enhance the anti-corrosion performance of inorganic silicate coatings through a threefold mechanism of filling, physical shielding, and electrochemical protection, which delays and prevents the penetration of corrosive media into the substrate surface. In addition, these fillers can also chemically bond with silicate matrix, thereby enhancing the adhesion and chemical stability of the coating. Layered fillers, such as mica powder, Ti₃C₂T_x, and layered double hydroxides (LDHs), provide the superior physical shielding and create a "maze effect" within the coating, which extends and convolutes the diffusion pathways of corrosive media like chloride ions and water molecules. This ultimately slows down the corrosion reactions of the substrate and improves the anti-corrosion performance of the coating.

In the micro-scale, the materials for the modification are mainly nano-scale fillers, such as nano-silica (SiO₂) and graphene-based nano-scale fillers. This review discusses the impact of modification materials in different scales on the performance of inorganic silicate coatings and elucidates their modification mechanisms. This review addresses the existing shortcomings of modification materials in various scales in current research and outlines the future development trends. Nano-SiO₂ enhances the bonding strength and anti-corrosion performance of inorganic silicate coatings via participating in the construction of the silicate network, thereby increasing the internal connectivity of the coating. Meanwhile, nano graphene-based fillers can improve the weather resistance and anti-corrosion performance of the inorganic silicate coatings due to their exceptional chemical stability, conductivity, and barrier properties.