The Role of Intumescent Coatings in Passive Fire Protection
Intumescent coatings have been a key strategy in the protection of buildings and other structures against fire for several decades. They form part of a passive fire protection strategy that might also include other materials such as concrete, mineral fibre boards, vermiculite, and cements.
In this article, we explore the effectiveness of intumescent coatings in providing passive fire protection for diverse types of structure, including offshore platforms and commercial buildings.
What Is Passive Fire Protection?
Fire protection in buildings and structures is crucial for safeguarding lives by delaying structural collapse which allows enough time for safe evacuation. It does this by either preventing fire or delaying the escalation of fire.
Active fire protection provides an immediate response to either suppress or extinguish a fire. Key components include fire alarms systems; sprinklers; suppression systems (such as foam and dry chemical systems); smoke control systems; and emergency lighting.
Passive fire protection (PFP) helps to prevent, withstand, and contain fire within a structure. These measures are integrated into the structure, and designed to protect the structural integrity of the building and provide occupants with sufficient time to evacuate safely. Key components of PFP include fire resistant materials; compartmentation (division of a building to contain the spread of fire and smoke using tactics like fire walls, fire doors, and fire-rated partitions); firestopping sealants; fire resistant insulation and intumescent coatings.
A Brief History of the Use of Intumescent Coatings
Intumescent coatings have been integral in protecting steel structures from fire for about 40 years. When exposed to fire, these coatings swell to create a protective barrier that can last up to four hours, significantly delaying the steel from reaching its critical failure temperature of approximately 400°C.
In the 1980s, the use of intumescent coatings saw a significant rise in Europe. Major oil companies recognised their ability to protect structural steel from the intense heat of hydrocarbon fires. This period also saw an increase in the use of exposed steel in commercial and high-rise buildings, which further boosted the demand for aesthetically pleasing, but simultaneously safe, coatings.
How Do Intumescent Coatings Work?
The chemistry of intumescent coatings involves several components:
- An organic binder resin (epoxy for hydrocarbon fires or acrylic for cellulosic fires)
- An acid catalyst (such as ammonium polyphosphate)
- A carbonific source (like pentaerythritol), and a spumific agent (e.g., melamine)
Upon exposure to fire, these ingredients react to form a low thermal conductivity carbon char that expands to provide a protective barrier. This char layer insulates the steel, reducing heat transfer and extending the time before the steel reaches its critical failure temperature.
Types of Intumescent Coatings
Intumescent coatings are categorised as thin-film or thick-film:
- Thin-film intumescents, often single-component solvent or water-based products which have dry film thicknesses (DFTs) of less than 5 millimetres.
- Thick-film coatings are typically solvent-free and epoxy-based which have DFTs up to 25 millimetres.
Recent advances have introduced multi-component methacrylate or ‘hybrid’ products, providing specific advantages over traditional formulations.
Which Type of Intumescent Coating Should Be Used?
Thin-film intumescents are typically used for aesthetic applications in commercial buildings, providing a paint-like finish. In contrast, thick-film coatings are used in more industrial settings, offering robust protection.
To specify the correct intumescent coating, it is essential to identify the item to be protected, such as structural steel or fire-resistant bulkheads.
The coating thickness depends on the steel’s weight and type, with lighter sections requiring thicker coatings for adequate protection. Determining the appropriate coating thickness involves calculating the steel’s shape and considering any irregularities. Manufacturers provide guidance for this and third-party certification ensures compliance with standards, ensuring optimal protection.
Common Applications for Intumescent Coatings
Intumescent coatings can be applied using various methods, including spraying. New hybrid products have expanded application possibilities, offering enhanced performance and flexibility. Typical situations in which intumescent coatings are used include:
· Commercial and Residential Buildings
Intumescent coatings are widely used in commercial and high-rise buildings to protect exposed steel, blending safety with architectural aesthetics.
· Industrial Facilities
In industrial settings, especially offshore platforms and floating facilities, intumescent coatings protect structural steel from the extreme heat of hydrocarbon fires, ensuring the integrity of critical infrastructure.
· Transportation and Marine Industries
These coatings are also used in transportation and marine industries, protecting against cellulosic and hydrocarbon fires, including jet fires resulting from high-pressure fuel releases.
Testing Intumescent Coatings
Given the variability in fire conditions, standardised tests offer a reproducible method to evaluate coating performance, ensuring reliability under different scenarios.
Intumescent coatings are subjected to standardised fire tests to ensure their effectiveness. Standards like BS 476 and EN 13381 for cellulosic fires, and UL 1709 and ISO 22899-1 for hydrocarbon fires, provide benchmarks for performance.
Further, to provide effective fire protection, intumescent coatings must be durable and intact when exposed to fire. Therefore, formulating these coatings requires careful consideration of moisture sensitivity and environmental resistance to prevent corrosion and ensure long-term protection.
Different resins are used based on the application environment. For example, water-based acrylics are suitable for dry, internal locations, while solvent-based epoxies are used for more demanding conditions. Standard tests like NORSOK M 501 and UL 2431 ensure these coatings meet durability requirements.
ICorr’s Passive Fire Protection Courses
To enhance understanding and application of passive fire protection, the Institute of Corrosion (ICorr) offers specialised Passive Fire Protection (PFP) courses. These courses provide in-depth knowledge on the principles of PFP, including the selection and application of intumescent coatings. Participants learn about the latest standards, testing methods, and best practices in ensuring the durability and effectiveness of PFP systems.
For example, the PFP Coating Inspector (Epoxy) Level 2 trains and examines Inspectors of Epoxy Intumescent Passive Fire Protection on the inspection of common types of epoxy coatings used to protect against hydrocarbon fires on installations for both on and offshore facilities.
ICorr’s courses are designed for professionals involved in fire safety and providepractical insights and certification to ensure the highest standards of fire protection in various industries.
Intumescent Coatings: The Bottom Line
Intumescent coatings provide critical passive fire protection, offering up to four hours of defence against fire. Applications range from commercial buildings to industrial facilities, ensuring safety and structural integrity across various environments. With advances in formulation and application techniques, intumescent coatings continue to evolve, enhancing fire protection capabilities in diverse settings.
If you’re looking to start or advance your career in PFP inspection, reach out to the admin team at ICorr or email IMechE Argyll Ruane to discover which of our specialised PFP courses is best for you.