Passive Fire Protection Methods- Intumescent Coatings

What is an Intumescent Coating?

An intumescent coating is a passive fire protection specialist paint that chemically reacts in a fire. The coating expandsin size to form a char, which protects the steelwork for a specified period of time from the heat of the fire.

Why do you need an Intumescent Coating?

The purpose of Passive Fire Protection and protecting structural steel is to give people inside the buildingtime to leave the building. Steel is a very strong and versatile building material, but at temperatures of 550C it begins to loose its structural integrity.

Intumescent for steel protection is commonlythick and opaque and finished with a thin protective fire retardant coat, like a gloss. Intumescent Coatings are normally applied by airless spray to provide a smooth decorative finish, which remains stable at ambient temperatures. . These coating compositions are based on organic resin binders, which are typically acrylated rubber or epoxy.


When dry, a passive fire protection intumescent coating is a reactive layer, so it is very immportantto achieve the correct thickness of dry film to obtain the required fire resistance. The film thickness is measured wet with a wet-film gauge, as a certain wet film thickness will dry to a specific dry film. Several coats may need to be applied to build up to a total dry coat thickness to give the required timeprotection.

The resins are filled with active ingredients, whichreact in a fire at temperatures around 250C to form a thermally insulating carbonaceous char or foam. The char can be expandedup to 50 times the original coating thickness.

As described above the basic formulation of an passive fire protection intumescent comprises of an organic binder, a carbonific, usually a penta or dipentaerythritol, a spumific or blowing agent which could be melamine or a melamine formaldehyde derivative, a source of an acid catalyst such as ammonium polyphosphate and additionally a char reinforcing pigment.

As the temperature risesthe binder begins to melt and the blowing agent liberates gases causing a controlled expansion. At the same time there is degradation of the carbon backbone and fusion of the inorganic reinforcing materials, resulting in char solidification.

In modernsteel and glass commercial buildings, exposed steelwork is sometimesan integral design feature. Intumescent coatings allow steel to be used as an designfeature (where fire protection boards would not) while also meetingto building regulations.

Intumescent passive fire protection coatings provide steel structures with corrosion protection, fire protection and a visualdecorative element if required.

Until recentyears, the typical airless unit for applyingintumescent coatings was a pneumatic pump having an air motor and capable of providing up to 4 - 5,000 psi at the pump. Such a unit requires a road compressor of about 150 cfm and is a heavy unit.

Improvements in passive fire protection intumescent formulation have reduced the weight of coatings and the need for high pressure application. Today, almost all intumescent coatings can be applied with a more compact self contained unit witheither a petrol engine or an electric motor.

In the UK, petrol engine units are more widely usedover electric because electric power is often not available on site at the early stage of construction when the intumescent is applied.

Special conditions:
Hydrocarbon fires tend to show a very fastrate of heating combined with extreme turbulence and result from the burning of hydrocarbon based fuels such asoil and gas. Therefore a specialpassive fire protection paint is required. Specialist intumescent coatings have been developed to cope with the aggressivenature of hydrocarbon fires, where resistance to blast overpressure and jet fire is a strong probability.

Oil and gas projects exist in some of the most aggressive environmental conditions and require not onlyfire protection but also exceptionally durable coatings. Epoxy intumescents are capableto provide not only the fire protection requirements, but also blast resistance and extreme durability to the worst weather conditions.

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