Intumescent Paint – Superior Fire Resistance for Steel Structures

intumescent paint for steel insulates steelwork from fire

Protect crucial structures with intumescent paint for steel

Strength is one of the main reasons we use steel in building construction. Steel is a tough construction material, used in buildings across the country from Golden Gate to Brooklyn Bridge. However, this strength is challenged by the severe heat of a fire. In a fire, it can take only minutes for unprotected steel to reach critical failure temperatures of 1000ºF, at which point it loses its load bearing capacity, leading to structural collapse. In fact, above 500ºF steel begins to lose strength. Which is why you should consider applying intumescent paint for steel structures.

Intumescent paint for steel is used in buildings, offshore structures, ships and aircrafts and it can provide the following advantages:

  • Allowing firefighters more time to get the fire under control
  • Extending crucial evacuation time
  • Fire protection for up to 120 minutes
  • Preventing structural collapse

In this article we will explain intumescent paint and outline the different types of intumescent coating for steel, how to comply with building resistance regulations, and where to find intumescent paint for steel products and contractors in the United States.


Intumescent paint for steel explained – How it works

The term ‘intumescent’ refers to a substance which increases in volume and decreases in density when exposed to high temperatures. Thus intumescent paint for steel is a fire barrier coating which, in the event of fire, forms a non-conductive carbon char to insulate the steelwork from the heat and flames.  The swelling reaction starts usually at about 200°F and the coating can expand up to 50 times its thickness. Intumescent coatings for steel can postpone structural collapse for up to 120 minutes; the different coatings are usually given 30, 60, 90, or 120 minute guarantee of fire resistance. Some industrial coatings guarantee fire protection up to 4 hours.

Standards and classification of intumescent steelwork coatings

Each building type requires different level of fire protection, and the intumescent steelwork coatings should be chosen by the required level. According to the national and international standards, materials (including paints) are classified based on the rate at which they allow flame to spread under test conditions. The intumescent paint fire rating classes go from Class A (best) to Class E (worst).

A certified inspector or architect usually defines which type of coating your building or structure requires. Once your coating is applied, you should obtain a certificate to show you have complied with all relevant regulations and used the correct protective surface coating. If you do not obtain the correct certificate(s) then, in the event of a fire, you may be held liable and prosecuted.


The 2 types – Hard and soft char intumescent coatings for steel

The main task of intumescent paint for steel is to create an insulating layer between the fire and the substrate to protect the steel from temperatures that might compromise its load bearing capacity. The intumescent paint thickness for steel is dependent on the required resistance and the type of coating used. Intumescent steelwork coating exists in two types: soft and hard char intumescent coatings.

1. Soft char intumescent coatings for steel

applying sherwin williams intumescent paint for steel

Thin film intumescent paint for steel is usually applied with a spray gun.

The soft char intumescent coatings for steel are also known as thin film intumescents. They are lightweight coatings which, when heated, create a foam-like char layer which is a poor conductor of heat and thus slows down the heat transfer. The char results from a chemical reaction between ammonium, polyphosphate, pentaerythritol and melamine; however, there are also other possible compositions; water and solvent based systems exist. The thin film intumescent coating for steel can be given a fire retardant topcoat to postpone the activation of the swelling reaction.

Uses: as intumescent steelwork coating on structural steel in constructions
Fire resistance: class A and B coatings for 30, 60 and 90 minutes protection (also industrial 120 minute coatings are available)
Expansion ratio: 50:1

2. Hard char intumescent paint for steelwork

The hard char intumescent paint for steel is also known as thick film intumescent paint due to the fact that it is applied in much thicker layers than soft char solutions. These intumescent coatings for steel were developed for combating hydrocarbon fires, however, nowadays they can be modified for other uses. These coatings are now also available in attractive yet limited color range. The char they form results from sodium silicate and graphite.

Uses: as intumescent paint for steel in harsh environments such as marine and offshore. Also used as intumescent paint for steelwork in exteriors of high rise buildings. Not suitable for interior use.
Fire resistance: class A coating for 90- 120 minutes fire protection (some industrial intumescent coatings up to 4 hours protection)
Expansion ratio: 5:1


Intumescent paint for steel in the USA – Manufacturers and contractors

There are many intumescent paint for steel products available on the US market. When it comes to the global manufacturers of intumescent paint Sherwin Williams, AkzoNobel, Jotun, FireOFF and Thermoguard are on the top. The coverage and fire resistance of intumescent coating for steel are dependent upon correct application. If you would like any more information regarding intumescent paint for steel, or would like to be connected with one of our partners for your project, contact us! Our experts are here to help, just use the “Request a quote” button at the bottom of this article and take advantage of our 100% free quote service.

Here below you can find several examples of the intumescent steelwork coatings available in the USA. The certified contractors also rely on for example AkzoNobel and Sherwin Williams intumescent paint products which are distributed to multiple intumescent paint suppliers. Note that the cost of intumescent paint is a sum of many factors; the coating type, film thickness, required resistance and application to name a few.

ManufacturerIntumescent Paint ProductIntumescent paint typeFire resistanceApplications
AkzoNobelInterchar 1120Waterborne, thin film intumescent paint for steelwork Up to 180 minutes as an independent systemArchitectural steel structures
FlameOFFFire Barrier PaintWaterborne, thin film intumescent paint for steel and other materials (eg. gypsum)Up to 120 minutesArchitectural steel structures, fire protection at home
JotunSteelmaster 60WBWaterborne, intumescent paint for steel beams and columns Up to 90 minutesFor structural steel exposed to cellulosic fires
PPGSteelguard 801Solvent based soft char intumescent paint for steelworkUp to 150 minutesSteel structures in infrastructure and powder generation
PPGSteelguard 702Solvent based soft char intumescent coating for steel (hollow sections)Up to 90 minutesHollow steel steelwork in infrastructure
Sherwin WilliamsFIRETEX M90/022K thick film (hard char) intumescent paint for steel in harsh environmentsUp to 240 minutesOnshore and offshore steel structures that require also corrosion protection.
Sherwin WilliamsFIRETEX FX5090Water based thin film intumescent coating for steel Up to 120 minutesCommercial construction; interior and exterior steelwork

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