Intumescent Coatings for Structural Steel Fire Protection

About this course.

An intumescent coating is a reactive paint-like material that stays inert at normal service temperatures but transforms when exposed to the heat of a fire. The short answer to how it protects steel is that, on heating, the coating swells to many times its original thickness and forms a lightweight, foam-like layer of carbon char. That char is a poor conductor of heat, so it acts as a thermal blanket that slows the rate at which the underlying steel warms up, buying time before the steel reaches the temperature at which it loses useful strength.

To understand why this matters, it helps to picture what happens to unprotected steel in a fire. Steel is strong, non-combustible and does not add fuel to a fire, but it is also an excellent conductor of heat and it softens as it gets hot. As temperature climbs, both its stiffness and its load-carrying capacity fall. Beyond a certain point the member can no longer safely carry its design load and may deflect, buckle or fail. Because a structural frame ties the whole building together, the failure of key columns or beams can lead to disproportionate collapse. Passive fire protection exists to delay that heating so the structure remains stable for a defined period.