Recycle of magnesium alloy scrap for improving fire resistance, thermal stability, and water tolerance of intumescent fire-retardant coatings

The rapid development and widespread application of magnesium alloy bring about a significant amount of magnesium alloy scrap. Thus, we offer a feasible and simple way to realize the recycling of magnesium scrap in this work, applying it as a synergist in the intumescent fire-retardant coatings for steel structure. With the introduction of magnesium scrap, the fire resistance, thermal stability, and water tolerance of the as-prepared coatings significantly improved. According to ASTM E119 standards, the fire resistance of coatings was investigated in our laboratory. Adding only ~ 0.48 wt% of the scrap decreased the backside temperature of the coated steel from 310°C to 171°C, with a ~ 44.8% reduction, indicating obvious synergy. Moreover, the coating containing ~ 0.48 wt% scrap exhibited excellent thermal stability and water resistance, and its char yield at 800°C and water contact angle reached up to 27% and 80.6°, respectively. Based on the analysis of flame-retardant mechanism, the scrap and intumescent fire-retardant system jointly promoted the formation of an intumescent and compact char residue, thus suppressing the heat transfer and protecting the steel. Hence, using magnesium alloy scrap as a synergist contributed to realizing the recycling of waste and providing practical intumescent fire-retardant coatings for structural steel.