Corrosion protection and fluorescence sensing of the europium complex-grafted short carbon fiber reinforced FEVE coating

Fluorocarbon resin (FEVE) coatings are widely used for metal corrosion protection due to excellent weatherability and chemical inertness. However, pristine FEVE coatings suffer from microporous defects, while short carbon fibers (SCF) as reinforcing fillers face poor interfacial compatibility and easy agglomeration in the resin matrix. Moreover, traditional coatings lack periodic corrosion monitoring capability. A multi-step surface modification strategy is proposed: SCF are synergistically modified with nitric acid (HNO₃) and a silane coupling agent (KH550) to obtain HK-SCF, improving surface activity and interfacial compatibility; then, a rare-earth europium complex Eu(phen)₂(NO₃)₃ is grafted onto HK-SCF to obtain fluorescence-functionalized HK-SCF@Eu, which is subsequently incorporated into FEVE to construct a fluorescence-sensing composite coating (HK-SCF@Eu/FEVE). Results indicate that synergistic HNO₃-KH550 treatment significantly increases surface roughness and functional group density of SCF, facilitating uniform grafting of the europium complex. At the optimal SCF content of 1.5 wt%, the composite coating exhibits the strongest fluorescence intensity, a tensile strength 38.8% higher than pure FEVE, an elongation at break of 67.7%, a corrosion current density of 3.59 × 10 −9 A·cm −2 , and a polarization resistance of 1.18 × 10 7 Ω·cm 2 . After 1440 h of salt spray and atmospheric corrosion testing, the coating demonstrates excellent long-term corrosion resistance. Furthermore, a linear relationship with R 2 = 0.982 is established between fluorescence intensity attenuation and corrosion time, enabling periodic visual monitoring of coating failure. This work successfully integrates fluorescence sensing into an FEVE-based coating, providing integrated corrosion protection and periodic monitoring for metal structures in marine engineering.