Corrosion protection mechanism of terephthalic acid-intercalated MgAlCe-LDH@MXene nanofiller-reinforced epoxy coating for steel rebar

In this study, terephthalic acid (TPA)-intercalated MgAlCe-LDH@MXene nanofillers were synthesized successfully and subsequently incorporated into an epoxy (EP) matrix to develop a TPA-MgAlCe-LDH@MXene/EP composite coating. The morphology, microstructure, and chemical composition of the synthesized nanofillers were characterized using SEM, XRD, FT-IR and XPS. The corrosion resistance of the composite coating was evaluated by immersing coated steel rebars in a simulated concrete pore (SCP) solution for 20 days, while the adhesion strength and mechanical properties were assessed through pull-off and nanoindentation tests. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations were performed to study the corrosion protection mechanisms of the nanofillers. The results showed that the adhesion strength, hardness, and elastic modulus of the composite coating were 1.37, 1.93, and 1.61 times higher, respectively, than those of the EP coating. The corrosion resistance was approximately three orders of magnitude greater than that of the EP-coated rebar. DFT calculations and MD simulations revealed that TPA molecules strongly adsorb onto the steel surface and form a protective layer. The outstanding corrosion protection performance of the composite coating is attributed to the synergistic effects of the physical barrier provided by the LDH and MXene nanosheets, the ion-exchange and inhibitor-reservoir functions of the LDH structure, the chemisorption film-forming capability of the TPA inhibitor, Ce 3+ -based cathodic inhibition, and the enhanced mechanical properties and adhesion strength.