Steel is a well-known material for its strength and durability in architecture and construction projects. However, steel’s susceptibility to high temperatures and fire is a significant challenge. This is where intumescent coatings come into play as a critical solution for enhancing the fire resistance of steel structures. These coatings, also known as intumescent paints, are a simple and effective way to protect the essential parts of a building, like columns, beams, floors, and roofs, from fire.
This coating helps keep the building from collapsing during a fire by insulating these structural elements. It provides the building with a certain amount of time to resist fire, which is crucial for safety. In this blog, we will discuss how they work, their applications, and considerations for use in construction. Let’s discuss it in detail!
How Is Intumescent Coating Applied?
Intumescent coatings are generally applied in three layers: a primer, a base coat, & a top coat. The primer helps the coating stick well to the metal and provides extra protection against rust. The top coat is sometimes added for looks or to make the coating last longer, especially in harsh weather or environments. Before applying it, the metal surface must be well-prepared and cleaned to remove any dirt or grease, creating a rough texture that helps the fire resistant coating stick better.
Nowadays, steel parts are often coated using an airless spray, a quick method that works well even on uneven surfaces. Brushes and rollers can also be used for application. Getting the coating thickness right on steel sections is tricky and depends on various factors like temperature and humidity. It’s important always to check the finished job’s quality and ensure it has the minimum thickness needed.
How Do Intumescent Coatings Work?
Steel’s critical temperature, defined as the point at which its load-bearing capacity is compromised by heat, typically ranges from 500 °C to 620 °C. However, this temperature can vary between 350 °C and 750 °C, depending on the structural loading conditions. This is why these coatings are particularly crucial for buildings with load-bearing steel elements, which can fail when exposed to high temperatures.
Upon exposure to heat, intumescent paint swells significantly, increases the volume of the fire resistant coating, and decreases its density, forming a ‘char’ layer that insulates the steel from the effects of the heat. These coatings are typically composed of three main components:
Binder: The component that forms the film and binds the other ingredients to the steel surface.
Flame Retardant: Generally, a phosphate that reacts to heat and forms a char.
Carbonific: A source of carbon that chars upon heating, contributing to the foam-like, insulating layer.
What Are the Factors to Consider for Intumescent Coatings for Steel?
When selecting and applying these coatings, it is important to consider various key factors to ensure optimal performance and compliance with safety standards. Below are some detailed considerations for choosing and using intumescent paints on steel frameworks.
Types of Coating
Intumescent coatings come in various formulations, each with specific characteristics suited to different conditions and requirements:
Water-based Coatings: These are environmentally friendly options that emit lower volatile organic compounds (VOCs) and should be lower than 36gr/liter. They are ideal for indoor applications where air quality is a primary concern after wildfires. These coatings are non-toxic and don’t create any fumes. Additionally, these coatings are ideal for industrial properties or areas requiring maximum durability and fire protection.
Solvent-based Coatings: These coatings typically offer better adhesion and durability in harsh environments. They are well-suited for exterior applications or areas with significant chemical exposure or varying temperatures. However, they do emit higher levels of VOCs compared to water-based alternatives.
Epoxy-based Coatings: These types of coating are known for their robust protective qualities. Epoxy-based intumescent paints provide excellent heat resistance and structural strength. However, a major disadvantage of solids-based epoxy is its extremely short pot life.
Thickness of Coating
The required thickness of intumescent paint depends on several factors:
Steel Section Size: The size and complexity of the steel sections play a crucial role in determining the thickness of the coating. Larger or more complex structural elements often require a thicker layer of intumescent paint to ensure they are well protected in a fire. The surface area exposed to heat and the volume of metal that needs to be insulated both influence the required thickness.
Fire Resistance Rating Desired: The thickness will also vary depending on the fire-resistance duration required (1-2 hrs generally). The longer the protection period required, the thicker the paint must be applied. This ensures that the steel beneath can withstand fire exposure without reaching its critical temperature for the duration specified. The coating manufacturer provides these specifications and must align with regulatory fire safety standards.
Assessment and Testing: It is important to refer to the technical datasheets provided by the paint manufacturers, which detail their products’ performance characteristics and application requirements. You can also consult with fire safety engineers for your construction project. These professionals can evaluate your project’s specific conditions and recommend the appropriate thickness based on empirical data and performance tests.
Compliance and Standards
Before applying these coatings, they must adhere to the following safety standards:
LEED v4–Compliant Paints: For projects aiming for LEED certification, selecting LEED v4–compliant intumescent coatings can contribute to earning points under the Indoor Environmental Quality credit category. These paints are specially formulated to lower volatile organic compound (VOC) emissions, improving environmental quality and occupant health.
ASTM Standard Testing: Adhering to ASTM standards for intumescent coatings is essential for ensuring high-quality fire protection and environmental safety. The ASTM standards establish critical benchmarks for the performance of fireproofing materials, offering a reliable measure of their effectiveness. By adhering to these standards, intumescent paints provide assurance regarding their fire-resistant characteristics and adherence to safety regulations. This builds trust among stakeholders and enables the creation of more resilient building solutions.
Wildland-Urban Interface (WUI) Compliance: In regions vulnerable to wildfires, particularly in the Wildland-Urban Interface (WUI), using intumescent paints that meet specific WUI regulations is important for enhancing building safety. These coatings are designed to resist the spread of fires from adjacent vegetation and natural areas, providing an additional layer of protection for structures in these high-risk zones.
Conclusion
By applying intumescent coatings, buildings benefit from an added layer of protection, substantially increasing their ability to withstand fire without structural failure. This not only ensures a higher degree of safety for occupants but also helps preserve the integrity of the building’s critical components during emergencies. At Firefree Coatings, we are committed to providing the most trusted intumescent coatings that are LEED v4 compliant and meet different ASTM standard requirements. Our products undergo rigorous testing, including Room Corner Tests, to ensure our coatings deliver unmatched protection and performance under extreme conditions. Call Us Today!
