1. Non-expansive fire-retardant coatings are mainly made of inorganic insulation materials such as expanded vermiculite, expanded perlite and mineral fibers. They are made of inorganic binders. They have good thermal insulation and bonding properties, stable physical and chemical properties, long service life and good durability. They should be selected preferentially. However, the non-expansive fire-retardant coatings have low strength and poor surface appearance, and are more suitable for concealed components.
2. Intumescent fire retardant coatings are mainly made of organic macromolecule materials. As time goes on, these organic materials may undergo irreversible reactions such as decomposition, degradation and dissolution, which make the coating "ageing" ineffective, resulting in powdering, peeling or swelling performance degradation. The extensive application of intumescent fire retardant coatings is mainly after 1990. At present, there are no quantitative indicators to directly evaluate the aging speed and life standard of the coatings. The service life of the coatings can only be judged from the comprehensive performance of the coatings. However, there are two points to be determined: first, the life of non-expansive fire-retardant coatings is longer than that of expansive fire-retardant coatings; second, the better the environmental conditions of coatings, the longer their service life. Therefore, the use scope of intumescent fire retardant coatings is limited in this code.
3. The environmental conditions of outdoor and semi-outdoor steel structures are more severe and disadvantageous than those of indoor steel structures. The requirements for water resistance, heat and cold resistance, light resistance and aging resistance of intumescent fire retardant coatings are higher. The steel structure of a large stadium canopy in China adopts an expansive fire retardant coating. After 10 years, the aging of the coating, performance degradation and shedding of the coating occur.
4. The particle size of expanded vermiculite and expanded perlite in non-expansive fire retardant coatings is generally 1 mm to 4 mm. If the thickness of coatings is too small, it is difficult to ensure the construction quality. Therefore, the minimum thickness of non-expansive fire retardant coatings is 10 mm.
5. Special attention should be paid to the compatibility between fire-retardant coatings and anticorrosive coatings, especially intumescent fire-retardant coatings, because they are organic materials as anticorrosive paints, and chemical reactions may occur. In the case that the third party certification material can not be issued to prove the compatibility of fire retardant coatings and anticorrosive coatings, the third party should be entrusted with the test verification. The construction sequence of intumescent fire-retardant paint and anticorrosive paint is anticorrosive primer, anticorrosive intermediate paint, fire-retardant paint and anticorrosive topcoat. The thickness of anticorrosive primer and intermediate paint should be controlled during construction, so as to avoid the falling off of fire-retardant coating due to the high temperature change of anticorrosive primer and intermediate paint, and to avoid the influence of too thick and too hard topcoat. The foaming expansion of intumescent fire retardant coatings.