A bio-based flame-retardant coating constructed from sodium alginate and tartaric acid derived from wine grape pomace

To enhance the thermal insulation and fire safety performance of 50SiMnVB steel, this study innovatively utilizes winery waste to extract tartaric acid (TA), achieving high-value conversion of waste biomass resources. By constructing a tartaric acid (TA)‑sodium alginate (SA) organic cross-linked network and incorporating aluminum hydroxide (Al(OH)₃) as an inorganic flame-retardant filler, an SA/TA/Al(OH)₃ composite flame-retardant coating was successfully fabricated on the steel surface, forming a high-performance fireproof and thermal insulation material. The results demonstrate that the SA/TA/Al(OH)₃-1 composite exhibits excellent flame retardancy, smoke suppression, and thermal insulation properties, as reflected in the following key metrics: a peak heat release rate (pHRR) of 2.21 kW·m^-2, total heat release (THR) of 1.72 MJ·m², peak smoke production rate (pSPR) of 0.00027 m²·s^-1, total smoke production (TSP) of 0.07 m², the limiting oxygen index (LOI) reaches 47.1%, and a char residue yield of 74%. when exposed to a 1300 °C butane flame, the temperature rise rate on the backside was reduced by 53.74%; the Raman spectroscopy ID/IG value of 0.0654 indicates effective enhancement of the thermal stability of the char layer. After 30 min of heating, the backside temperature was only 162.7 °C, with a thermal conductivity as low as 0.083(W/m^-1·k^-1). The coating also demonstrates good mechanical properties, with a compressive strength of 14.3 MPa. Utilizing bio-based waste materials, this strategy synergistically enhances flame retardancy, thermal insulation, and eco-friendliness, offering a sustainable pathway for developing high-performance green protective materials.