Bi-functional epoxy coating with long-term protection for Q235 steel prepared by incorporating melamine-grafted and carbon-black-modified graphene oxide

In recent years carbon materials, such as graphene oxide (GO) and carbon nanotube, have been became key materials for high-performance coatings for the protection of metals from corrosion. Here, a novel bi-functional epoxy coating was developed and formulated, which can replace traditional primers and topcoats. Furthermore, the effects of modified graphene oxide‑carbon black (MGC) on the corrosion resistance and weathering resistance of coated Q235 samples have been investigated using salt spray testing, UV accelerated aging testing, and electrochemical impedance spectroscopy. Results suggest that the incorporation of MGC leads to a considerable enhancement in the corrosion resistance and weathering resistance of coated samples. Notably, the bi-functional epoxy coating formulated with 0.2 wt% of MGC demonstrated the most effective anti-corrosion and weathering resistant properties. During the UV accelerated aging testing for 20 days, the low-frequency impedance modulus values of bi-functional epoxy coated samples were recorded to be 1.09 × 108 Ω·cm2, which is higher than pure epoxy coated samples (9.05 × 106 Ω·cm2). Also, the highest adhesion strength of bi-functional epoxy coated samples decreased from 2.51 MPa to 1.97 MPa. These observations suggest that the bi-functional epoxy maintained a significant portion of its adhesion strength even after undergoing UV accelerated aging, indicating its robustness and durability under such corrosion conditions.