Influences of montmorillonite on fire protection, water and corrosion resistance of waterborne intumescent fire retardant coating for steel structure

Organic-modified montmorillonite (OMMT) was used as nano-layer filler to improve the fire protection, water and corrosion resistance of waterborne intumescent fire retardant coating. The influence of OMMT on the properties of fire retardant coating and the mechanism of OMMT effect on the coating were investigated in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric (TGA) analysis, Fourier transform infrared spectroscopy (FTIR), fire protection test, water and corrosion resistance test. It was found by XRD that OMMT could be exfoliated and dispersed well in the coating with the addition of 1 wt.%, while excessive OMMT was easy to aggregate and dispersed badly. SEM micrographs and EDS analysis results showed that well-dispersed OMMT nano-layers were parallelly distributed in the coating. The results of fire protection test and the observation results of morphology of char layers indicated that the fire protection of the coating and foam structure of the char layer were remarkably improved by adding suitable content of OMMT. TGA analysis demonstrated that OMMT could enhance the combustion residual weight and thermal stability of the coating. Based on the results of water and corrosion resistance test, the parallel-arranged OMMT could significantly slow down the migration and solvation of fire retardant additives through its barrier effect, thereby improving the water and corrosion resistance of the coating.