- Calcium borate is an inorganic compound composed primarily of calcium (Ca²⁺) and borate (BO₃³⁻ or related polyborate anions) ions, with the general chemical formula often represented as Ca₂B₆O₁₁·5H₂O in its hydrated form.
- It occurs naturally as the mineral colemanite, one of the most important borate ores. Calcium borate typically appears as a white or colorless crystalline solid or powder and is sparingly soluble in water but more soluble in acidic conditions. It is valued for its flame retardant, anti-corrosive, and antifungal properties, making it useful across a range of industrial applications.
- One of the major uses of calcium borate is in the glass and ceramics industry, where it functions as a fluxing agent. It lowers the melting point of raw materials during glass production and improves the thermal and mechanical properties of the final products. It enhances the durability, chemical resistance, and clarity of glass, particularly in specialty borosilicate glasses used in laboratory equipment, cookware, and insulation materials. In ceramics, it helps control the melting behavior and surface finish of glazes.
- In flame retardant formulations, calcium borate acts synergistically with other materials to suppress combustion. It promotes the formation of a protective char layer and inhibits the release of flammable gases during thermal decomposition. These properties make it suitable for use in plastics, textiles, and building materials that require enhanced fire resistance. Additionally, calcium borate is used as a wood preservative, where it helps protect against fungal decay and insect damage without introducing high toxicity levels, making it a more environmentally friendly alternative to traditional treatments.
- In agriculture, calcium borate serves as a source of boron and calcium, two essential micronutrients for plant growth. Boron is crucial for cell wall formation, membrane function, and reproductive development in plants, while calcium supports cell wall structure and nutrient transport. Calcium borate is used as a slow-release boron fertilizer, particularly in soils with low boron availability, providing sustained micronutrient supply without the risk of toxicity associated with more soluble borate compounds.
- Calcium borate is also used in metalworking, lubricants, and anti-corrosion coatings. In these applications, it acts as a stabilizing or buffering agent, improving product performance and longevity. Its inclusion in greases and cutting fluids helps reduce friction and wear, while in coatings it provides protective barriers against environmental degradation.
