What is Intumescent Coating for Steel?

Intumescent coating, or paint, is designed to swell to 50 times its own thickness when subjected to temperatures over 120°C. As the coating swells it forms a carbon layer which thermally insulates the steel structure it is protecting. The goal of an intumescent paint  application is to keep high temperatures, caused by fire, away from the steel members for between 30-120 minutes.

The critical failure point for the structural steel framework of a building is between 550 – 620°C. Once the steel reaches these temperatures it will begin to buckle and bend, with a high risk of collapse. The purpose of intumescent coating is to maintain the steelwork below this temperature, in a condition of ‘elasticity’. This describes a state in which the steel will bend or deflect, but will crucially return to its original form once the heat reduces.