What is Intumescent Paint Coating – How Does it Work?

You may have heard of the term “intumescent coating” but may not be familiar with what it really means.

Simply put, an intumescent coating or an intumescent paint is a protective layer of a substance that gets activated with a chemical reaction generated from heat application. 

When exposed to extreme temperatures (exceeding 120°C), these coatings will react and expand on the surface, forming a thermally insulating layer with or without the release of water.

This means, in addition to their corrosion protection, intumescent paints are also fire-retardant and are therefore used for fire protection and insulation of steel substrates that are prone to get exposed to fire.

How Intumescent Coating Works?

The intumescent materials (like graphite and sodium silicate) used in the paint soften out, increase their overall volume and get reduced in density when exposed to intense heat sources or fire.

The result is a fire-retardant hard insulating layer or a substrate protector that’s produced in the form of a carbonaceous char accompanied by a non-flammable gas.

The layer swells up to 50 times the thickness of the paint in a controlled manner and is designed in such a way that it thermally insulates the material for a specific period of time, ranging from 30 to 120 minutes.

Depending on the material and coating specification, most of them will protect your assets for 30 minutes to 4 hours during a fire.

Choosing Different Kinds of Intumescent Paint

Intumescent paints are available in a wide variety of formulations and can be applied to structural load-bearing steel, timber, composites, plaster, and concrete structures alike.

When selecting the formula, consider whether the intumescent paint is required for interior or exterior use, fire resistance levels (FRRs), and the type of material that needs to be painted, as each formulation and brand provides unique benefits at varied costs.

For building materials, ASTM E119 (UL 263) and E84 (UL 723) are among the most commonly accepted standards. So, to fireproof your premises with the utmost security, ensure that the formula comes with proper fireproofing compliance.

Besides that, go for the products that are environmentally friendly, contain low VOCs, and are EPA compliant; this is especially required if your premises need to meet EPA standards.

Above all, factor the cost of the intumescent paint formula and its corresponding application into your project budget.

The cost of intumescent coating may vary depending on the brand, required coverage, coating thickness and adhesion, and the outcome you need. But in general, you should expect to pay anywhere between $4 and $15 per square foot.

Why and Where are Intumescent Coatings Needed?

During a blaze, it is essential to shield the structural integrity of buildings, or else there could be devastating consequences.

Intumescent paint does exactly this by decreasing fire spread, allowing for more time to evacuate safely and consequently potentially saving lives.

Keeping the vital materials from reaching their critical failure temperature also prevents building collapse.

• The critical temperature for steel, for example, is the temperature at which the element can no longer support the applied loads and is very close to collapsing. Depending on the load and other conditions, it varies from 350 °C to 750 °C.
• When it comes to concrete, the critical state is determined by its reinforcing bars’ critical temperature (which can range from 350 °C to 500 °C).
• For wood-based structures, however, the critical state is defined by how much load-bearing timber component remains after burning.

Intumescent paint coatings not only protect steel and similar surfaces from the heat and flames of fire but also has other uses as well, like…

• Gasketing
• Creating window casings
• Protection against corrosion and rust
• Fireproof door frames in buildings and offices
• Retarding or slowing down the advancement of heat sources 

Because graphite and sodium silicate are relatively cheap and easy to find, intumescent paint that contains such substances are widespread and used on a variety of objects created from steel and other similar materials, such as ships, aircraft, automobiles, etc.

Tips for Maximum Fireproofing with Intumescent Coating

When applying intumescent paint, you can use a sprayer, paint brush, or roller, depending on the manufacturer’s instructions.

Also, use PPE (including eye protection, a respirator, gloves, and a pair of overalls) to cover your whole body during the application.

To ensure that your finish looks flawless, it is important to prepare the surface properly by getting rid of any dust, dirt, or rust with either sandblasting or pressure washing prior to the application of intumescent coating.

Usually, there is a need for an underlying primer, but some products offer a 2-in-1 solution that includes both primer and top coat. It’s good to check out your product’s technical info before starting.

After the application, intumescent paint generally dries within 2-8 hours, though this timeframe is subject to change based on factors such as coating thickness, applicator used, and working conditions.

Can Intumescent paint be used for wood?

When using paints and coatings to fireproof lumber, we must consider the difference between fire-retardant paint and intumescent paints.

While fire-retardant paints are created to reduce a blaze’s burn rate – in turn limiting flames spreading throughout an area – they do not protect (or insulate) its substrate from potential damage.

Intumescent paints, on the other hand, offer both resistant properties as well as insulation for their base material; when exposed to heat. These specialized coatings expand, forming a protective char coating against any sparks or flame which may be present, giving precious moments to prevent the substrate from burning.

Before applying your preferred coating to the wood structures, clear out any dust, dirt, debris, or paint, and make sure all surfaces are smooth and clean. Also, take into account the thickness of the intumescent coating that needs to be applied.

Different manufacturers have different instructions regarding this, and you should check out the information based on the choice of using a primer, paintbrush, roller, or airless paint sprayer.