Fig. 1. (a) SEM image of raw h-BN. (b) SEM image of h-BN fillers obtained via ultrasonication. (c) TEM image of raw h-BN. (d) TEM image of h-BN fillers with some flake-like h-BN debris.

Fig. 2. (a) Photographs of the BN-P paint sat for 0 day and 7 days (from left to right: BN-P0, BN-P0.025, BN-P0.05, BN-P0.1, BN-P0.15, BN-P0.02, BN-P0.25). (b) Stable structure of PVB adsorbed on h-BN surface in methanol (Pink: B atom; Blue: N atom; gray: C atom; White: H atom; Red: O atom). (c) Oxygen-nitrogen and (d) oxygen-boron radial pair distribution function.

Fig. 3. (a) Polarization curves of PVB coatings modified with different amounts of h-BN fillers (h-BN ≤ 6.98 wt.%). (b) Corrosion rate of copper substrate beneath BN-P coatings obtained by Tafel analysis. (c) Linear polarization plots of the BN-P coatings. (d) Linear polarization resistance (Rp) of the BN-P coatings.

Fig. 4. (a) Bode modulus and (b) Bode-phase plots of the PVB coatings modified with different amounts of h-BN fillers after immersion for 8 days. (c) Schematic diagram of the equivalent circuit used for EIS data fitting. (d) Fitting results of the coating resistance (Rc).

Fig. 5. Bode phase and modulus plots of BN-P coatings after immersion in 3.5 wt.% NaCl aqueous solution for 22 days. (a)(b) BN-P0; (c)(d) BN-P0.025; (e)(f) BN-P0.05; (g)(h) BN-P0.1; (i)(j) BN-P0.15; (k)(l) BN-P0.2; (m)(n) BN-P0.25; (o) Proposed mechanism of the enhanced corrosion protection performance of the BN-P composite coatings.

Fig. 6. Time-dependent coating resistance Rc of the blank and BN-P coating.

Fig. 7. (a) Photograph of the experimental samples before and after immersion in 3.5 wt.% NaCl aqueous solution. (b) Photograph of the experimental samples before and after immersion after removing the coating.

Fig. 8. Metallographs of the experimental samples before and after immersion for 1 and 2 months in 3.5 wt.% NaCl aqueous solution. (bar = 30 μm).

Fig. 9. Raman spectra of copper substrates coated by different BN-P coatings after immersion in a 3.5 wt.% NaCl aqueous solution for (a) 1 and (b) 2 months.

Fig. 10. Fitting results of the charge transfer resistance (Rct) of the copper beneath scratched BN-P coatings after immersion in a 3.5 wt.% NaCl aqueous solution for 4 days.

Fig. 11. SEM images and photograph of the scratched coating samples. (a) BN-P0; (b) BN-P0.025; (c) BN-P0.05; (d) BN-P0.1; (e) BN-P0.15; (f) BN-P0.02; (g) BN-P0.25 (bar =200 μm). (k) Photograph of scratched BN-P coatings after 4 days of exposure to a 3.5 wt.% NaCl aqueous solution (from left to right, the h-BN loading increases from 0 to 11.1 wt.%).