Anti-corrosion and flame-retardant properties of environmentally benign smart functionalized WS2/rGO in epoxy coatings for enhanced steel structural protection in natural seawater

Abstract

The epoxy matrix (EP) was filled with the rGO-APOD/WS2 nanofiller that was generated through mixing the surface-modified WS2 with reduced graphene oxide (rGO) and 2-amino-5-(4-aminophenyl)− 1, 3-oxadiazole (APOD). The effectiveness of epoxy coating on mild steel as a barrier against various concentrations of rGO-APOD/WS2 in naturally occurring seawater was assessed using EIS, SECM, and salt spray tests. In order to achieve the best coating performance, it was found that the optimal weight ratio of rGO-APOD/WS2 in the EP matrix was 0.3. The limiting oxygen index (LOI) test showed that the rGO-APOD/WS2 considerably enhanced the flame retardancy properties of the epoxy coating. In comparison to pure epoxy coating, the EP-rGO/APOD-WS2 demonstrated better flame retardancy with considerable reductions in the values of PHRR and THR, i.e., 81% and 70%, respectively. It was discovered that the coating resistance of EP-rGO/APOD-WS2 was much higher (Rcoat: 9.89E10 kΩ.cm2) than that of pure matrix (1.49E5 kΩ.cm2) after being exposed to natural seawater for one hour. The EIS experiments showed that the EP-rGO/APOD-WS2 nanocomposite had increased coating resilience even after 200 h of submersion in seawater. Because the coated substrate is more resistant to anodic dissipation than the uncoated substrate, SECM investigations showed that the least quantity of Fe2+ ions discharged at the scratch of the EP-rGO/APOD-WS2 coating. WS2 was found in rusted parts, producing an excellent inert layer at the surface, according to FE-SEM/EDX investigation. The newly created EP-rGO/APOD-WS2 composite has higher barrier and hydrophobic characteristics, according to the results (WCA:162°). The epoxy matrix's mechanical properties were enhanced by the addition of rGO/APOD-WS2. It was discussed how graphene-based polymer nanocomposites might prevent corrosion. As a result, an industrial coating made of the EP-rGO/APOD-WS2 nanocomposite may be used.