Intumescent Coatings
Intumescent coatings are reactive coatings used to minimise the effects of a fire. Applied to structural steel, they swell to form a layer of inorganic carbonaceous char when exposed to temperatures above 250ºC.
This insulates the steel from the heat, enabling it to maintain its load-bearing capacity for longer. As a result, there is more time for evacuation of the building and emergency response, potentially saving lives.
There are a number of factors to consider when specifying intumescent coating systems, including both fire duration and durability, to ensure that the system is fit for purpose in the event of a fire.
When intumescent coating systems are specified, ‘fire duration’ (i.e. the amount of time that the system will enable the steel to maintain its load-bearing capacity during a fire) is often the key consideration. Typically, fire duration ranges from 30 minutes to 120 minutes. The fire duration required for a specific building depends on a number of factors and is often set by local building codes.
However, another key consideration – durability – cannot be overlooked. Durability is the ability of the reactive coating system to maintain an adequate level of fire protection after exposure to environmental conditions, either during the construction phase or during end-use. It is very important that durability is predicted correctly, as premature weathering or aging of the coating system may have a negative effect on the intumescent coating’s fire protection properties.
Both fire duration and durability should be taken into account when specifying the full system. Intumescent coating systems usually comprise several layers of different paints: a two-coat system (primer + intumescent) may be sufficient for low corrosive environments; a three-coat system (primer + intumescent + topcoat) may be preferred for more corrosive environments.