Thin Nacre-Biomimetic Coating with Super-Anticorrosion Performance

The rigorous organic and inorganic laminated structure of nacre has been developed by millions of years of biological evolution against various external impacts, including mechanical loadings and chemical attacks. Nacre-biomimetic materials have been recognized as an effective strategy to achieve high strength and toughness simultaneously. However, the understanding of nacre-like structure from the perspective of corrosion protection is still very limited. This work investigates the anticorrosion performance of nacre-biomimetic GO/epoxy (NBGE) coatings with alternating layers. Potentiodynamic polarization measurements indicated that the corrosion rate of steel protected by the NBGE coating with 5 layers of GO and 6 layers of epoxy (5NBGE) and a total thickness of 17 μm was 20 times slower than that of steel under the pure epoxy coating twice as thick in 3.5 wt % NaCl solution. Electrochemical impedance spectroscopy measurements revealed the importance and functions of the GO layers in NBGE coatings. The 5NBGE coating exhibited better performance than carbon-based nanoparticle/epoxy mixed coatings. The superior anticorrosion performance of the NB5G6E coating was supported by photographic observations, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chloride diffusion measurements. The strong cross-linking layer-by-layer structure of NBGE coatings was proved by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses. The anticorrosion mechanism of the NBGE coatings was interpreted by the mitigation of chemical reactions occurring at the steel-coating interface due to the restricted intrusion of O2, H2O, and Cl- through the reduced pores and defects by the intercalated GO layers in the coatings.