Types of fire protection coatings
Fire protection coatings are classified into 4 categories:
1- Neutral paints
2- Fire retardant coatings (Intumescent paints)
3- Retardant moisturizers
4- Spray-applied fire-resistive materials (SFRMs) Neutral paints
These paints are set of resins, pigments or moisturizers that are not flammable and do not result in the spread of fire. Most of resins are flammable but the existence of nitrogen, bromine and chlorine atoms in the resin structure reduces flammability of resin. In general, emulsion paints (with water solvent) and mineral-based paints such as cementitious or silicate paints will not be flammable, if they have mineral and fire resistant pigments (such as antimony oxide and zinc borate) but they cannot protect the substrate against fire. Fire retardant coatings (Intumescent paints)
When these coatings exposed to heat, a series of chemical and physical reactions are carried out which can delay burning of the surface. Fire retardant coatings are combined with free radicals on the substrate and they create a layer which is resistant to fire. Also, non-flammable gases and water vapor are produced at high temperatures which under these conditions, the heat transfer is reduced. Halogenated materials extinguish the fire through absorbing active radicals produced at high temperatures and converting them into less active radicals.
Fire retardant coatings are in a form of paints or varnishes which are used in industrial and constructional steel structures, installations and etc. Retardant moisturizers
Retardant moisturizers are materials that penetrate into the pores of wood or fibers and delay the spread of flame. These materials are mostly ammonium salts such as ammonium sulfate, ammonium bromide and ammonium dihydrogen phosphate which are decomposed into ammonia, water and phosphoric acid in the vicinity of fire. After applying retardant moisturizers, a suitable paint is applied to the substrate. Spray-applied fire-resistive materials (SFRMs)
SFRMs are based on minerals such as vermiculite, perlite, phosphates, borates, silicates, carbonates, oxides and chlorides of magnesium, iron and zinc. Slag wool, gypsum and Portland cement are the other ingredients of spray-applied fire-resistive materials. In the presence of these coatings, flame does not reach to the substrate. The minerals contained in these coatings form a melting layer that absorbs heat and leads to lower temperatures.