Pre Painted Galvanized Steel

The "fireproof" function of the pre painted galvanized steel, more accurately, refers to its fire resistance and fire integrity. pre painted galvanized steel does not mean that the material will not burn at all, but can effectively delay the spread of the flame, inhibit the combustion process, and maintain the structural integrity for a period of time in case of fire, so as to obtain valuable time for personnel evacuation and fire rescue.

The fire prevention function of the pre painted galvanized steel is mainly realized through the synergistic effect of the following three aspects:

The core of pre painted galvanized steel is flame retardant coating:

The pre painted galvanized steel can realize the most direct and critical link of fire protection function. By adding special flame retardant to the finish and back paint of the pre painted galvanized steel when encountering flame, the coating will have a series of physical and chemical reactions:

·pre painted galvanized steel has heat absorption and cooling function: some flame retardants (such as aluminum hydroxide and magnesium hydroxide) will decompose when heated and absorb a lot of heat, so as to reduce the temperature of pre painted galvanized steel surface and delay the time to reach the ignition point.

·pre painted galvanized steel forms thermal insulation carbon layer: flame retardant can promote the coating to expand and carbonize at high temperature to form a dense and porous carbonized layer. This carbonized layer acts as a "thermal barrier", which can not only isolate the oxygen below, but also block the heat transfer from the flame to the base plate (steel plate).

·Dilution of oxygen and combustible gas: some flame retardant will generate incombustible gas (such as water vapor, carbon dioxide, nitrogen, etc.) when decomposing. These gases can dilute the concentration of oxygen and combustible pyrolysis gas on the material surface, so as to inhibit combustion.

·Interruption of combustion chain reaction: some halogenated or phosphorous flame retardants can capture free radicals generated during combustion, interrupt the chain reaction of combustion and "extinguish" the flame from the chemical level.

Type of fire retardant coating of pre painted galvanized steel :

·Intumescent fire retardant coating: this is the most common and efficient. In a fire, the coating will expand dozens or even hundreds of times to form a thick foamed carbon layer, so the thermal insulation effect is excellent.

·Non-expansive fire retardant coating: it is mainly used for heat insulation and oxygen isolation through its high melting point, low thermal conductivity or glass film generated after being heated.

Foundation: metal base plate

The base plate of pre painted galvanized steel (usually galvanized steel plate, aluminized zinc steel plate or aluminum-magnesium manganese plate) itself is non-combustible material (Class A). This is the physical basis of its fire protection function.

·Not involved in combustion: metal substrates do not become fuel, which are fundamentally different from wood, plastic, and other materials.

·Provide structural support: In a fire, even if the organic coating on the surface is burned, the metal substrate can maintain its shape and strength for a certain period of time to prevent the building components from premature collapse.

Overall: fire resistance of pre painted galvanized steel system

When the pre painted galvanized steel is processed into the roof panel or wall panel and installed on the building structure, its fireproof performance shall be considered as a system. This includes:

·Insulation behind colored rolls: If the system includes insulation (e.g. rock wool, glass wool), the fire rating of these materials (which shall be Class A incombustible material) is essential. High-quality fireproof color steel plate is often combined with rock wool to form "rock wool sandwich plate", and its overall fire endurance can reach more than 1 hour.

·Installation and connection mode of pre painted galvanized steel : lapping between plates and fixing mode between plates and purlins will affect whether flame and high temperature flue gas may spread through gaps.

Part 2: Examples

For better understanding, we illustrate several specific application scenarios and product types:

Example 1: Industrial plant and logistics warehouse

·Scenario description: A large logistics warehouse with a large number of goods, including inflammable goods. Once a fire occurs, it spreads very fast.

·Application products: rock wool sandwich board or pre painted galvanized steel veneer with high performance fireproof coating.

·Fire protection function:

·Prevention of lateral spread of fire: if the warehouse roof or wall is provided with fireproof pre painted galvanized steel , in case of local fire, the flame will not quickly ignite the adjacent plates. The flame retardant coating forms a char layer that limits the flame to the initial area.

·Protection of building structure: metal base plate and internal rock wool core material can effectively block high temperature, prevent the fire from burning the roof structure in a short time, resulting in overall collapse, and create conditions for personnel escape in the warehouse and firefighter's internal fire fighting.

·Comply with building codes: such buildings are usually required to use building materials with fire resistance rating not less than 1 hour. Fireproof pre painted galvanized steel is a common solution to meet this requirement.

Example 2: Non-bearing exterior wall of high-rise building

·Scene description: Modern high-rise buildings widely use color coated plates as curtain walls or decorative lines. Building exterior wall fires have a "chimney effect" and spread extremely quickly (refer to the lessons learned from the Glenfield Tower fire in London).

·Application product: Class A fireproof metal composite plate.

·Fire protection function:

·Eliminate flame spread along the facade: Class A fireproof color coated composite plate, with non-combustible mineral wool as the core material and metal plate with fireproof coating on both sides. Even if a fire occurs indoors, it is very difficult for the flame to break through the outdoors and spread upwards along the exterior wall.

·Ensuring overall safety: this application strictly limits the use of combustible materials on the facade of the building and is the mandatory requirement focus of the current global building fire protection code.

The fire protection function of the pre painted galvanized steel is a system engineering, which combines:

·Chemical protection (flame retardant coating realizes active protection through heat absorption, char formation, vapor phase suppression, etc.)

·Physical protection (non-combustible metal substrate provides final structural support)

·System integration (form effective fire barrier together with insulation materials and connection structures)

When selecting the fireproof pre painted galvanized steel , do not just listen to the word "fire prevention", but pay attention to its specific fire rating certification (such as Class A and B1 in Chinese GB 8624 standard, or A2, B-s1, D0 in EU EN 13501-1 standard) and fire resistance limit test report (such as GB/T 9978) to ensure that it meets the safety requirements of specific building projects.