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Passive fire protection and insulation – Intumescent paint for steel

The New Zealand steel industry produces steel for construction, infrastructure, storage, manufacturing, and farming. Steel is the backbone of construction; its strength and durability holds up many of our buildings, from dairy sheds to the Sky Tower in Auckland. Though steel may not burn, temperatures of 300°C and above will weaken steel and, once the structural strength is lost, this leads to building collapse. Fire protection coatings are one way of protecting steel from fire. Intumescent paint for steel is becoming the industry passive fire protection coating of choice because it:

  • Provides vital extra time for evacuation and fire crews – The coating adds up to 120 minutes of fire resistance to a substrate, allowing more time for fire detection, building evacuation, and for fire crews to get the blaze under control.
  • Protects the substrate from structural weakening and collapse – Intumescent paint reacts at temperatures of approximately 200°C, insulating the substrate from the heat extremes.
  • Is easy to apply – Intumescent paint is applied by spray at varying film thicknesses, can be solvent- or water-based, on-site or off-site, and can be overpainted if required.

In this article we look at how intumescent paint for steel works, its different applications, and where to find intumescent coating products and contractors in New Zealand.


The science behind intumescent paint

The reason intumescent paint is the steel industry go-to is not just its powerful fire protection properties. Outside of chemical fires, it is not the flames that pose a threat to the steel, it is the heat. So, how does intumescent paint work?

Intumescent paint for steel reacts to heat by swelling and insulating the substrate.

The swelling reaction of intumescent paint insulates the steel from the damaging heat.

  1. When exposed to the heat of a fire a reaction is triggered and intumescent paint expands or swells to up to 50 times its original thickness, forming a layer of solid foam-like char.
  2. The char is very slow burning – this provides up to 120 minutes of extra time for firefighters to get the situation under control and for buildings to evacuate.
  3. The char is insulating – this protects the substrate from being damaged by the heat of the fire and, in the case of steel, prevents it heating to temperatures above 300°C where it begins to lose structural strength.

For steel substrates, the highest level of fire protection is through a duplex system. This combines the flame-damping properties of a fire retardant coating with the insulation of an intumescent. With a fire retardant top coat, the flames are kept at bay for even longer, delaying the intumescent coating’s reaction and adding crucial extra time.

Applying intumescent paint for steelwork – thick and thin film

Intumescent coatings are divided by application method and also by the length of time they provide fire protection for – 30, 60, 90, or 120 minutes. Building regulations require different minimum time requirements which vary depending on building type. Intumescent coatings for steel can be divided into two broad families: thin film and thick film. Thin film materials are either solvent based or water based and are mainly used for building fires. Thick film coatings were originally developed for the off-shore and hydrocarbon industries but have been modified for use in buildings.

Thin film intumescent coatings for steel

Thin film fire rated paint for structural steel generally has three components, a primer, a basecoat, and a sealer coat. These paints are mainly used for 30, 60, and 90 minutes. Thin film materials have a 50:1 expansion ratio; a 1mm thick coating will expand to about 50mm in a fire. These coatings are bother solvent- and water-based, and are available in a range of finishes.

Thick film intumescent coatings for steel

Thick films have a higher dry film thickness than thin film coatings, and are usually epoxy based. Originally developed for use with hydrocarbon fires, thick film materials are now also used in harsh or difficult to maintain environments where thin film materials would not work. Examples include external steel in high rise buildings and exposed marine environments. Expansion ratios are typically about 5:1, and attractive finishes are also possible.

Hydrocarbon and cellulosic passive fire protection

Not all fires are the same, and the location of the fire will determine the speed and heat of the blaze. Hydrocarbon fires are those that burn because of a combustible liquid or accelerant like petrol or chemicals. They burn hot and extremely fast. Cellulosic fires are those where the fuel source is cellulose – wood, cardboard, paper, cotton, and similar materials. They take longer to reach their peak heat than a hydrocarbon fire, and will not burn as hot. There are also jet fires (a special type of hydrocarbon fire) and rapid rise fires (tunnels, nuclear fires).

Knowing the type of fire that your property is likely to experience is important for choosing the right intumescent paint system. Coating manufacturers develop intumescent coatings as solutions for specific grades of fire protection, climate and exposure, and application techniques. Cellulosic passive fire protection is ‘Category 1’ and hydrocarbon passive fire protection is ‘Category 2’. Commercial and architectural installations like tall buildings, stadiums, or bridges are usually Category 1, while industrial and offshore installations like refineries, oil and gas platforms and chemical plants include the more heavy duty Category 2 protection.


Where to find intumescent paint for steel specialists NZ

Intumscent paint should always be applied by a professional. A trained contractor can provide effective and Standards-compliant coating that is certified and meets all requirements. There are intumescent painting contractors and businesses across the country. Below is a sample list of intumescent painting contractors and businesses in New Zealand. A professional application is not just about peace of mind – you need certification for a fire protection coating once the job is done.

If you need intumescent coating for your project, get in touch! Our experts are here to help. We can connect you with the right coating and the right specialists for your needs. Take advantage of our 100% free quotation service and let us know about your project requirements to get the ball rolling by using the “Request a Quote” button beneath this article. In collaboration with our coating partners, we will determine the best match for your requirements.

The top intumescent paint manufacturers and products in NZ

Intumescent CoatingFire Protection CategoryProduct Description
Chartrek 7Category 2 – Hydrocarbon Pool and Jet Fire ProtectionEpoxy intumescent with jet fire certification for durations of up to 3 hours. Tough, durable and resistant to impact and vibration damage. Provides long term corrosion resistance. NORSOK M501 compliant. Suitable for steel, aluminium, and other substrates.
Interchar 3120Category 1 – Cellulosic Fire ProtectionModified epoxy intumescent providing up to 120 minutes of fire protection. Designed for off-site application to structural steelwork. Suitable for environments up to C5. BS 476 certified.
Jotun SteelMaster 60WBCategory 1 – Cellulosic Fire ProtectionThin film, water-based intumescent for 30, 45, 60, and 90 minutes fire protection of structural steel and carbon steel. Suitable for environments up to corrosivity category C3. BS 476 certified.
PPG STEELGUARD 581Category 1 – Cellulosic Fire ProtectionFire protection for 30, 60, or 90 minutes. Resistance for C1 and C2 exposure conditions. BS 476-20/21 certified. Water-based formulation.
PPG STEELGUARD 560Category 1 – Cellulosic Fire ProtectionFire protection for 30, 60, 90, or 120 minutes. Resistance for C1, C2, C3, and C4 exposure conditions. BS 476-20/21 certified. Solvent-based formulation.

Professional intumescent coating contractors in New Zealand have a wide range of products and companies to choose from when sourcing their coatings. These companies and their intumescent products include:

  • AkzoNobel – International Paints Interchar range
  • Altex Coatings – the Nullifire range of intumescents, and Pro-Seal
  • Firepro – Firepro C696, S605, S606, and S707
  • Jotun – the Steelmaster range (120SB, 60SB, 60WB, 1200WF)
  • Phoenix – Phoenix Intumescent 370-60, 370-90, 370-120, and 170-120
  • PPG – the Steelguard range (851, 801)
  • Resene Paints – the Fireshield system
Intumescent Paint SpecialistLocationServices Offered
Advanced ApplicatorsChristchurchIntumescent coatings for steel in construction, infrastructure, and contracting
Cake Commercial ServicesAuckland, Wellington, and Christchurch branchesThick and thin film intumescent coatings for commercial projects, water- and solvent-borne
Global FireAucklandIntumescent paint for steelwork
Jeff Dermott Painting and Decorating LtdChristchurch and Auckland branchesIntumescent paint for steel for residential, commercial, and industrial projects
Ranger Specialist CoatingsTimaruIntumescent paint applicators
RedCrow Passive Fire ProtectionAuckland and Wellington branchesIntumescent coating for structural steel
TBS GroupBranches New Zealand-wideIntumescent coating for steelwork in commercial buildings, structural steel, and more
Topcoat Specialist CoatingsAuckland, Otago, and Christchurch branchesFireproofing coating applications including intumescent paint for steel
Walter Bowden PaintersAucklandApplicators of intumescent paint for steel in commercial and industrial buildings

Fire resistance ratings and building type

The fire resistance requirements of your building depend upon a range of factors. Building use and building height are the two most important factors. High rise buildings with high occupancy have high fire resistance requirements, as do hospitals. A Fire Resistance Rating (FRR) describes the length of time a building element needs to resist fire in different categories. For example, FRR 60/60/60 means the component has fire resistance of 60 minutes for resisting structural collapse, 60 minutes for integrity to resist the passage of flame, and 60 minutes of insulation to resist the transfer of heat to a specified level. For a closer look at New Zealand fire resistance regulations and fire paint for steel and other substrates visit out fireproof coatings overview.


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