Reaction principle of inorganic coatings

　　The reaction principle of inorganic coatings is mainly based on the chemical reaction between the inorganic binders (such as silicate, potassium silicate, silica sol, etc.) in their components and carbon dioxide and water in the air, forming a stable coating structure. The following are the specific reaction mechanisms and key points:

　　I. Core Reaction Principle: Mineral Petrification Reaction (Carbonation Reaction)

　　The film-forming process of inorganic coatings is a chemical bonding process, unlike the physical film-forming of traditional organic coatings (such as resin solvent volatilization and curing). Taking silicate inorganic coatings as an example, the reaction principle is as follows:

　　1. Alkaline Environment of the Substrate Surface

　　Inorganic coatings are usually used on alkaline substrates such as cement and lime (pH ≥ 10). During construction, the water-soluble silicates (such as sodium silicate and potassium silicate) in the coating penetrate into the pores of the substrate in the form of an aqueous solution.

　　2. Reaction with Carbon Dioxide (Carbonation)

　　The silicates in the coating react chemically with carbon dioxide (CO₂) and water (H₂O) in the air to produce insoluble calcium silicate (or potassium silicate) gel and calcium carbonate (CaCO₃).

　　The generated silicate gel will tightly fill the pores of the substrate, forming a strong mineral coating that chemically bonds with the substrate as one, with extremely strong adhesion.

　　Calcium carbonate, as a byproduct, further enhances the hardness and stability of the coating.

　　3. Continuous Curing and Strength Improvement

　　The reaction process proceeds gradually over time, and the coating will continue to harden. The water resistance, scrub resistance, and other properties will increase with the degree of carbonation (usually requires more than 28 days for complete curing).

　　II. Key Characteristics and Influencing Factors of the Reaction

　　1. "Homogeneity" with the Substrate

　　Inorganic coatings form a mineral community with the substrate through chemical reactions, rather than simple adhesion, therefore:

　　Strong crack resistance: It is not easy to crack with the thermal expansion and contraction of the substrate;

　　Good breathability: Moisture inside the substrate can evaporate through the pores of the coating, avoiding blistering and peeling.

　　2. Necessity of Alkaline Environment

　　The reaction depends on the alkalinity of the substrate (pH ≥ 10). If the substrate alkalinity is insufficient (such as old walls), an alkaline primer should be used in advance, otherwise the coating cannot be effectively cured.

　　3. Influencing Factors of Curing Speed

　　Humidity: Moderate humidity (50%~70%) is conducive to CO₂ dissolution and diffusion, accelerating the reaction; extremely dry or humid environments will slow down curing.

　　Temperature: Low temperature (<5℃) will inhibit the chemical reaction, and construction should be carried out at a suitable temperature.

　　Coating thickness: Too thick a coating may lead to insufficient internal reaction, affecting overall performance.

　　III. Comparison of Principles with Organic Coatings

　　IV. Application Scenarios and Precautions

　　1. Applicable Substrates

　　Cement, concrete, brick walls, lime mortar, and other alkaline substrates;

　　Not suitable for non-alkaline surfaces such as metal and wood (requires special treatment).

　　2. Construction Points

　　The substrate should be clean, dry, and firm, with pH ≥ 10;

　　Avoid construction on rainy days or under high temperature and strong light to avoid affecting the reaction process;

　　Alkaline primer is usually required to enhance adhesion.

　　3. Maintenance Advantages

　　Old coatings can be directly renovated without complete removal (the chemically bonded layer is compatible with the new coating).