Intumescent coatings are widely used in the field of fire protection. Their performances can be affected by various weathering causes such as UV exposure, moisture, temperature or immersion in corrosive environment such as seawater. This study investigates the weathering of a model epoxy based intumescent thick coating, containing ammonium polyphosphate (APP), melamine and titanium dioxide, designed to improve the fire resistance of steel in case of hydrocarbon fires. The coating was exposed to accelerated UV-light exposure, to humidity combined with heating and to immersion tests in distilled and salted water. UV-light, humidity and temperature only slightly affect the protective efficiency of the coating. Immersion in distilled water for one month however shows a slight decrease of the protective properties. This was explained by the fact that, on coating extreme surface, APP turns into polyphosphoric acid, which, combined with the mechanical erosion effect of water, is dissolved in water. When immersed one month in the salt water bath, the fire protection was totally lost and intumescence was not observed. The mechanisms involved in the loss of fire protection by the salt water, investigated using Electron Probe MicroAnalysis (EPMA) X-Ray mappings as shown in the Figure1, will be further discussed during the conference.

Weathering of intumescent coatings for passive fire protection

248th National Meeting (2014)

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