Ablative Coatings for Structural Fire Protection

If ablative coatings are used to protect reentry vehicles under severe aerodynamic heating, why can they not be used to protect structural steel in fires? To answer this question, it is necessary to define ablation, to explore the nature of the thermal effectiveness of ablative materials, and to investigate the problems associated with the use of ablative materials for structural fire protection. A clear understanding of the differences between aerodynamic reentry atmospheres and the fire atmospheres is also important. All these factors are discussed. Several ablative systems presently used in aerospace applications along with specially formulated systems were evaluated in an idealized fire atmosphere. These high-performance aerospace ablative systems are not satisfactory for fire atmospheres from both a thermal and economic standpoint. However, other systems are presently available that yield sufficient char for thermal protection. The limitations of these systems is primarily in the cost of the raw materials and susceptibility of these systems to cracking.