Steel Structure Fireproof Coating - Intumescent & Inorganic Fire Protection

Fireproof principle of steel structure fire retardant coating

1. The indoor fireproof coating for steel structures is flame-retardant or non-combustible in itself. It keeps the protected substrate from direct contact with air, thus delaying ignition and slowing down combustion speed.

2. Besides being flame-retardant or non-combustible, steel structure fireproof coating features low thermal conductivity, which delays heat transfer from flame to the protected base material.

3. When heated, indoor fireproof coatings decompose to release non-flammable inert gases, which dilute combustible gases produced by the protected objects, making them hard to burn or slowing down the combustion rate.

4. Nitrogen-containing fire retardant paint decomposes into groups such as NO and NH3 when heated. These substances combine with organic free radicals to terminate chain reactions and reduce temperature.

5. Intumescent steel structure fireproof paint expands and foams when heated, forming a carbonaceous foam thermal insulation layer to enclose the protected components. It delays heat transfer to the base material and prevents ignition combustion as well as strength reduction caused by temperature rise.

Indoor fireproof coating for steel structures is inherently flame-retardant or non-combustible. It isolates the protected base material from direct air contact, delaying ignition and slowing down combustion.

Nitrogen-containing fireproof paint decomposes into radicals such as NO and NH3 under high temperature, which combine with organic free radicals to stop chain reactions and lower the temperature.

Intumescent fireproof paint for steel structures expands and foams when heated, forming a carbon foam thermal insulation layer to cover the protected parts. It slows heat transmission to the base material and prevents combustion as well as strength decline caused by rising temperature.

Main characteristics of steel structure fireproof coating

The steel structure fireproof coating enables the expanded carbonized layer to possess excellent adhesion and strength. It can stay well attached even under strong airflow impact, completely solving the problem of carbonized layer peeling off.

The technical introduction of steel structure fireproof coatings states that to protect users' property of steel structure components from losses, different types of such coatings are recommended for different steel structure projects.

1.Ultra-thin Steel Structure Fireproof Coating

Ultra-thin steel structure fireproof coating refers to the one with coating thickness within 3 mm (including 3 mm). It features good decorative effect, expands and foams at high temperature, and generally has a fire resistance limit within 2 hours.

This type of coating is mostly solvent-based, boasting excellent bonding strength, outstanding weather resistance, water resistance, good leveling property and fine decoration performance. When exposed to fire, it expands and foams slowly to form a dense and firm fireproof thermal insulation layer with strong fire impact resistance, which slows down the temperature rise of steel and effectively protects steel components.

It can be constructed by spraying, brushing or rolling, and is commonly used for building steel structures requiring fire resistance limit within 2 hours. New varieties with fire resistance reaching or exceeding 2 hours have been developed. They are mainly compounded with specially structured polymethacrylate or epoxy resin mixed with amino resin and chlorinated paraffin as base binders, high-polymerization ammonium polyphosphate, dipentaerythritol and melamine as fire retardant system, added with inorganic refractory materials such as titanium dioxide and wollastonite, and blended with No.200 solvent oil.

It is widely applied for fire protection of light steel structures and space trusses. Its ultra-thin coating greatly reduces usage amount compared with thick and thin type fireproof coatings, cutting down total project cost while providing efficient fire protection with excellent fireproof effect.

2.Thin-coat Steel Structure Fireproof Coating

It refers to fireproof coatings with coating thickness over 3mm and no more than 7mm. It has certain decorative effect, expands and thickens under high temperature, with fire resistance limit within 2 hours.

It is generally made of suitable water-based polymers as base materials, combined with composite flame retardant systems, fireproof additives and refractory fibers, sharing the same fireproof mechanism as ultra-thin type. The selected water-based polymers shall feature good adhesion, durability and water resistance to steel substrates.

It has better decoration performance than thick-type coatings yet inferior to ultra-thin ones, with fire resistance limit mostly within 2 hours. It is widely used for steel structure fire protection projects requiring fire resistance within 2 hours and mainly applied by spraying. It once occupied a large market share, yet it has been gradually replaced by ultra-thin steel structure fireproof coatings.

3.Thick-type Steel Structure Fireproof Coating

This coating has a thickness ranging from over 7 mm to 45 mm, featuring granular surface, low density and low thermal conductivity, with a fire resistance limit of more than 2 hours.

Composed mainly of inorganic materials, it delivers stable fireproof performance and favorable long-term service effect. However, its large particle ingredients lead to uneven coating surface, which affects architectural appearance, so it is mostly applied to concealed structural works.

In case of fire, it slows down the temperature rise of steel components by virtue of its granular texture, low density, low thermal conductivity and heat absorption property, so as to protect steel structures.

It is formulated with proper inorganic binders such as water glass, silica sol, aluminum phosphate and refractory cement, mixed with lightweight inorganic thermal insulation aggregates, fireproof additives, chemical agents, reinforcing materials and fillers, enjoying the advantage of low cost.

Commonly constructed by spraying, it is suitable for indoor and outdoor concealed steel structures, high-rise full steel buildings and multi-storey factory steel structures that require fire resistance over 2 hours. For instance, columns of high-rise civil buildings and multi-layer supporting columns in general industrial and civil buildings need to reach a 3-hour fire resistance limit, which requires the protection of this thick-type fireproof coating.

4.Mineral Wool Building Fireproof and Thermal Insulating Coating

It is another important type of building fireproof coating developed after perlite series and magnesium oxychloride cement series thick fireproof coatings, which is still under further promotion. Compared with perlite-based fireproof coatings, its core advantage is that mineral fibers used as thermal insulation fillers can reinforce coating strength. It is applicable to earthquake-prone areas and buildings subject to frequent vibration, and delivers fire prevention, thermal insulation and sound absorption effects.

Main varieties include mineral fiber fireproof thermal insulation coatings and thermal insulation fillers. It is mainly composed of mineral wool with cement as the common binder. Dry spraying is adopted on construction sites: dispersed fibers and binders are conveyed to the nozzle via high-pressure air, then mixed with highly atomized water around the nozzle and sprayed onto the construction surface.

It forms low-density coatings to reduce building overall weight and structural load. Fast-drying mineral wool fireproof coatings are widely used abroad, featuring easy construction, low cost and short drying time even under harsh construction conditions.