Novel multilayer epoxy nanocomposite coatings for superior hydrophobic, mechanical and corrosion protection properties of steel

Abstract

A novel multilayer polymeric epoxy coating consisting of 3-(2-aminoethylamino) propyl dimethoxy methylsilane (AEAPS), Mo2C and graphene oxide (GO) was synthesized. The graphene oxide wrapped molybdenum carbide was examined by SEM/EDX, TEM, and XRD. The protective performance of epoxy-GO/AEAPS-Mo2C coating on mild steel was evaluated in 3.5% NaCl solution by EIS, polarization, and SECM studies. The optimum percentage of graphene oxide embedded Mo2C nanoparticles in the epoxy matrix was found to be 2.0 wt% in which the coating has the least aggregation and higher coating resistance. The EIS measurements showed an enhanced coating resistance of EP-GO/AEAPS-Mo2C nanocomposite (7301.75 kΩ·cm2) after 360 h of immersion compared to plain epoxy (1.05 kΩ·cm2) coatings. Moreover, it was also found that the coating resistance of EP-GO/AEAPS-Mo2C was 49.93% higher than that of pure matrix after 1 h immersion. SECM measurements confirmed that the least dissipation of ferrous ions was observed at the crack of the EP-GO/AEAPS-Mo2C nanocomposite coated steel specimen (1.4 I/nA) due to the improved resistance for anodic dissipation of the coated substrate. FE-SEM/EDX examined that Mo was reinforced in the degradation products which formed an excellent passive layer at the coating/steel interface. The results showed that the newly developed EP-GO/AEAPS-Mo2C nanocomposite coating possessed superior corrosion protection and enhanced hydrophobic behaviors (WCA: 152°). The investigated coatings showed profound mechanical properties. The hardness value was found to be 1290 MPa for EP-GO/AEAPS-Mo2C nanocomposite while the value of the pure epoxy coated specimen was 275 MPa. The inclusion of graphene oxide wrapped molybdenum carbide in the epoxy matrix displayed superior mechanical properties in term of adhesion strength and hardness.