One article to understand fireproof paint for steel

22 / 07 / 2022

One article to understand fireproof paint for steel
Steel structures are widely used in the modern construction industry because of their light weight, high strength, large span, large space, good seismic performance, convenient hoisting and construction, and short construction time.
In public buildings and commercial construction, such as airports, high-rise and super-high-rise buildings, exhibition halls, gymnasiums, swimming pools and other public buildings, such buildings are densely populated areas where steel structures are used and have clear fire protection requirements.
From the perspective of building life, there are high requirements for the durability of fireproof coatings, and fireproof coatings with reliable quality should be selected.

Before we start, let’s find out what is fire retardant coating?

Fire retardant coating is a kind of coating applied to steel structures and building surfaces, that can produce fire and heat insulation. It can reduce the flammability of the building surface, and also has the effect of retarding the spread of fire, which is mainly used to improve the fire resistance level of the raw materials to be coated.

So what are fire retardant coating for steel structure and what are its types?

Steel fire retardant coatings can have different classification methods according to different characteristics:

1. According to the application, fire retardant coating for steel structures is divided into:

Exterior fire retardant coating and interior fire retardant coating
The difference between outdoor fire retardant coating and indoor fire retardant coating:
-The outdoor fireproof coating has more indicators than the indoor fireproof coating, which requires heat resistance, humidity and heat resistance, and freeze-thaw cycle resistance.
- Exterior Fire retardant coatings can be used both outdoors and indoors, while interior fire retardant coatings can only be used indoors, not for outdoor.


2. According to the medium, steel fire retardant coating can be divided into:

Water-based steel structure fireproof coating and solvent based steel structure fireproof coating

3. According to the thickness of use, steel structure fireproof coatings can be divided into ultra-thin and thin-coating and thick-coating fireproof coatings

- Ultra-thin fireproof coating for steel structure: refers to the coating thickness within 3mm, the thickness of this coating is better for decoration, and it will expand and foam at high temperature, and the fire resistance limit is generally within 2h, Ultra-thin steel structure fireproof coatings are generally used in house structure and factory buildings

- Thin steel structure fireproof coating: refers to the coating thickness of more than 3mm and less than or equal to 7mm, the decorative effect is slightly worse than the ultra-thin type, expansion and thickening will occur when the temperature rises, and the fire resistance limit is generally within 2h (for steel base Has good adhesion, water resistance and durability
- Thick coating steel structure fireproof coating: refers to the thickness of the coating thickness greater than 7mm and less than or equal to 45mm, the surface is granular after painting, and the appearance of the coating is uneven, which affects the overall appearance of the building, so it is mostly used for structural concealment projects. . The density is relatively small, the thermal conductivity is low or the material in the coating is heat-absorbing, which delays the temperature rise of the steel, and the fire resistance limit is generally above 2 hours


4. According to the fire protection mechanism, the steel structure fireproof coating is divided into: steel intumescent fireproof paint; non-intumescent steel fireproof paint.

-Intumescent fireproof paint:
After film formation, intumescent paint is an ordinary steel paint film at room temperature. However, the fireproof coating expands and carbonizes, forming a non-flammable sponge dozens or even hundreds of times larger than the original thickness under the action of flame or high temperature. Intumescent fireproofing coating can cut off the heating of the substrate by the external fire source, so as to play the role of flame retardant and heat insulation.
- Non-intumescent steel fireproof paint (thick fireproof coating):
Non-intumescent paint does not expand and foam when it encounters high temperature, and it is a fireproof coating for steel structure with a fire-resistant and heat-insulating protective layer.
The working principle of non-intumescent fire protection paint is to reduce or delay the speed of flame temperature conduction to the main body of the steel structure, thereby delaying the collapse time of the steel structure, saving lives and property losses to the greatest extent, its own flame retardancy and non-combustibility; it can release fire-extinguishing gas under flame or high temperature and form Non-flammable, no base layer to isolate the air.

How does intumescent coating protect steel?

Steel structure, as a non-combustible building material, under the high temperature of fire, its mechanical properties such as yield strength, tensile strength and elastic modulus decrease with the increase of temperature. When the temperature rises to about 500 °C, its mechanical strength will decrease by 60%, bending deformation occurs, and the loss of Bearing capacity, resulting in the bending of steel columns and beams, and the collapse of buildings.

In case of fire, the coating expands and foams to form a carbonized refractory thermal insulation protective layer, which delays the heating rate of the steel structure and avoids the rapid heating of the steel structure, thereby improving the protection of the fire resistance time limit of the steel structure.
In order to prolong the bearing capacity of the steel structure under fire and high temperature, it is most practical, simple and convenient to spray the fireproof coating directly on the steel components.

Steel structure fireproof coating has good fireproof and heat insulation performance, construction is not limited by the geometric shape of steel structure, generally does not need to add auxiliary facilities, and the coating quality is light, and it has a certain aesthetic decoration effect. Among them, the intumescent fireproof coating will foam and expand under the action of high temperature, forming a carbon-based thermal insulation layer with a thickness of tens to hundreds of times the thickness of the original coating.
The temperature of steel structures not protected with intumescent fire retardant coatings can rise rapidly to 500°C within 15 minutes. The carbon-based thermal insulation layer formed by the intumescent fire retardant coating can maintain the bearing capacity of the steel structure for up to 120 minutes, thereby gaining more time for escape.

Jointas has launched two indoor steel structure intumescent water based fire retardant paint. JT615 1.5 hours intumescent fire proof paint and JT620 2 hours fire rated intumescent paint.
Jointas steel intumescent fireproof paint is a one-component and use emulsion as binder and water as dispersion medium and various flame retardants, foaming agents and carbon-forming agents.
Jointas Intumescent steel paint has properties of safe and environmental protection, non-toxic, low VOCs, no chemical reaction with any anti-corrosion primer, and no irritating odor.

Intumescent fire proof paint is used for fire protection and protection of indoor exposed steel beams such as airports, power plants, stadiums, commercial plazas, industrial plants, and high-rise buildings.
Here is the video of fire retardant paint for structural steel

With more high-rise buildings and stricter fire regulations, the industry needs high-quality, high-performance solutions for modern buildings

Jointas is a national high-tech enterprise specialized in making water-based coatings for steel structure, petrochemical equipment, container, construction, home decoration, and asphalt coating, etc.
If you have more questions about anti corrosion paint for steel in your project, just feel free to contact us, our expert team will help you with solutions. Email:

What are the characteristics of indoor fireproof coatings for steel structures?

1. Heat insulation:

The flame retardant coating of steel structure fire retardant coating can be decomposed into non-flammable inert gas when heated, and has low thermal conductivity, which may delay the transfer of flame temperature to the protected substrate, thus reducing the speed of burning.

2. Good adhesion

Fireproof coating has a good adhesion to the steel surfaces and not easy to fall

3. Flame retardancy:

The fireproof material itself has flame retardancy or non-combustibility, which can prevent the protected sheet from immediately contacting the gas, delay the ignition of the block and reduce the rate of ignition.

4. Good compatibility and no corrosion with primer

5. Economical and practical:

Spraying 2-3mm fireproof coating to steel will have fireproof effect, which can reduce the total cost of the project

6. Rapid expansion:

The steel structure fireproof coating expands and foams rapidly in case of fire. The expanded carbon layer is dense and not easy to fall off, which blocks the spread of the fire and buys time for rescue

7. Excellent water resistance

8. Green and environmentally friendly

How to distinguish the quality of intumescent steel structure fireproof coating?

The role of fireproof coating for steel structure: through construction, the fire resistance time of the building can be effectively improved, so it is very important to know how to distinguish the quality of intumescent steel structure fireproof coating.

Qualified fire retardant coatings will foam and expand a lot when burned by a strong fire such as a blowtorch, and the surface will gather and bulge, and there will be no burning damage after a few minutes. If the slag is scattered and slag is scattered, the substrate will also be burnt and damaged quickly.


How do you apply intumescent paint to steel of JT615 and JT620?

1. Before the fire retardant coating is applied, the rust removal and anti-corrosion primer coating on the surface of the steel structure should meet the design requirements and the current relevant national regulations, and the dust, oil and other sundries on the surface of the steel structure should be completely removed. Fire retardant coating should be carried out before interior decoration and under the condition that it will not be damaged by subsequent works.
2. During construction, the walls, doors and windows, mechanical equipment and other components that do not require fire protection should be shielded and protected.
3. This product is suitable for painting by brushing. Before painting, the paint should be stirred evenly. If the paint is too thick, an appropriate amount of water can be added to dilute it until it is suitable for brushing and does not flow.
4. The thickness of the first pass of brushing should be able to cover the layer. Generally, it should not exceed 05mm but should not flow. After the coating sprayed in the previous pass is basically dry and solidified, spray it again. The general interval 8~24h, until the desired thickness.
5. After spraying to the desired thickness. After curing for 30 days, spray a top coat on the surface of the fire retardant coating.
6. This product can also be painted by spraying method, and the coating steps are basically the same as the dry brushing method.
7. During the construction process and before the coating is dried and cured, the ambient temperature should be kept at 5~45°C, the relative humidity should not be greater than 90%, and the ventilation should be maintained. When there is condensation on the surface of the component, it is not suitable for construction.
8. This product is a water-based fire retardant coating, so the coating should be placed indoors or in a rain shelter during or after the construction to avoid rain.