A facile strategy to fabricate an intumescent fire-retardant coating with improved fire resistance and water tolerance for steel structure

An intumescent fire-retardant coating (IFRC) with improved fire resistance and water tolerance was prepared in this work, resulting from the introduction of microcapsuled ammonium polyphosphate (MFAPP) and zinc borate (MFBZ). The as-prepared coating exhibited great fire resistance and smoke suppression. In the cone calorimetry test, adding only 6 wt% MFBZ dramatically reduced the peak heat release rate, total heat release, and total smoke release by ~ 23.4%, ~ 54.7%, and ~ 81.1%, respectively. In addition, the water resistance and thermal stability of the coatings were also characterized. The char yield of IFRC noticeably increased to 41.7%, indicating good high-temperature stability. Besides, the IFRC showed a water contact angle of 90.1° and maintained good structure and fire resistance after being soaked by water, indicating great water resistance. The enhanced performance portfolio was mainly due to the synergistic effects of ammonium polyphosphate, pentaerythritol, melamine, and zinc borate, and the hydrophobicity of melamine–formaldehyde resin (MF). This work offers an effective approach for the preparation of waterborne intumescent fire-retardant coatings with great fire resistance and water tolerance. Graphic abstract