The Importance of Fireproof Coatings for Steel Structures

1. Compensate for the fire resistance defects of steel structures: Although steel has high strength, it has high thermal conductivity and softens easily when exposed to fire. Ordinary steel structures lose their load-bearing capacity in about 15 minutes during a fire, while fireproof coatings can form a protective layer through insulation or intumescent foaming, delaying the steel's temperature rise and buying time for evacuation and firefighting.

2. Meet building fire protection code requirements: According to the "Building Design Fire Protection Code," steel structures in different building types must achieve corresponding fire resistance limits (e.g., steel columns in high-rise buildings require a fire resistance limit of 2-3 hours). Fireproof coatings are a key measure to achieve this requirement.

3. Reduce fire damage: They can reduce the risk of steel structure collapse, protect the facilities and structural integrity inside the building, and lower post-disaster repair costs.

Classification of Fireproof Coatings

Protection Targets and Fire Resistance Performance

• Ordinary steel structure fireproof coatings (Fp): For ordinary industrial and civil buildings (fiber-type fires)

• Special steel structure fireproof coatings (Ft): For special buildings such as petrochemical facilities, substations, etc. (hydrocarbon fires)

• Fire resistance limits: 0.5h, 1h, 1.5h, 2h, 2.5h, 3h

 

Marking of Fireproof Coatings

For example:

GT-WRP-Ft2.00-A: Outdoor solvent-based intumescent fireproof coating, special steel fire resistance limit 2 hours, company code A

GT-NSF-Fp1.50-B: Indoor water-based non-intumescent fireproof coating, ordinary steel fire resistance limit 1.5 hours, company code B

Design and Selection of Fireproof Coatings

• The fire protection design for steel structures should select the corresponding category of fireproof coatings based on the building or structure's use, location, fire type, and fire resistance limit.

• Intumescent steel structure fireproof coatings contain organic binders, catalysts, foaming agents, and charring agents. When exposed to fire, the organic substances undergo a series of physical and chemical reactions, rapidly expanding to form a dense honeycomb carbonaceous foam insulation layer. However, over time, some organic substances undergo irreversible processes such as decomposition, degradation, and leaching, causing the coating to "age" and fail, resulting in powdering and peeling. The coating's durability is poor, and performance degradation is significant. Tests show that within 5 years, the fire resistance limit decreases by 21.7%.

 

• Non-intumescent steel structure fireproof coatings are made with porous lightweight insulating materials (such as vermiculite, perlite, mineral fibers, etc.) as aggregates and binders. Since the main components are basically inorganic, the coating's physical and chemical properties are stable, with a long service life. Projects with over 20 years of application have not found failures.

 

 

Summary

• For places and components with high fire resistance requirements (fire resistance limit ≥ 2 hours), non-intumescent fireproof coatings are recommended, and non-epoxy intumescent steel structure fireproof coatings are not recommended.

• Epoxy intumescent steel structure fireproof coatings have excellent adhesion, weather resistance, and fire protection performance, and are not restricted by usage location.

 

 

Mesh Requirements During Construction

(1) If the type test report of the fireproof coating indicates mesh reinforcement, mesh construction should be applied during engineering use. Mesh materials should preferably be iron wire mesh, alkali-resistant fiberglass mesh, or carbon fiber mesh.

(2) If the type test report does not indicate mesh reinforcement, but the coating is relatively thick, mesh construction measures should be taken and should comply with the following provisions:

1. For non-intumescent steel structure fireproof coatings with a coating thickness greater than or equal to 25mm, mesh construction should be applied within the steel structure fireproof coating.

2. For non-epoxy intumescent steel structure fireproof coatings with a coating thickness greater than or equal to 3mm, and epoxy intumescent steel structure fireproof coatings with a coating thickness greater than or equal to 8mm, mesh construction should be applied within the steel structure fireproof coating.

• When applying fireproof coatings on galvanized steel components, a primer should be sprayed on the galvanized parts to enhance the adhesion of the fireproof coating.

Comparison Chart of Advantages and Disadvantages of Fireproof Coatings