Composite materials. Enamel is a composite material with corrosion resistance, high temperature resistance, wear resistance and insulation, and smooth and clean surface, which is coated with glassy inorganic materials and sintered at high temperature.

Enamel materials are made of metal and glassy inorganic materials and fired at high temperature. Metal and glassy inorganic materials are different in many physical and chemical properties, even contradictory; For example, metal has good ductility and can be cold-worked into products of various shapes, while glassy inorganic materials have poor ductility and cannot be cold-worked and formed; Metals have poor chemical resistance, especially acid resistance, while glassy inorganic materials have strong chemical stability and acid resistance. Metal is a good conductor of electricity, while glassy inorganic materials are insulators; Metals have large thermal conductivity and thermal expansion coefficient, while glassy inorganic materials have small thermal conductivity and thermal expansion coefficient. These two materials with completely different properties can make up for each other's shortcomings and reflect their respective advantages by coating and firing into a whole.