Fig. 1 Potentiodynamic polarization curves of GNPs/Mg composites in SBF

Fig. 2 Metallographic structure diagrams of GNPs/Mg composites: a No. 1, b No. 2, c No. 3, d No. 4. e SEM image and X-ray mapping of No. 4 with 0.9 wt% GNPs: f Mg, g Al, h C

Fig. 3 a SEM image of No. 2 with 0.3 wt% GNPs. b The corresponding magnification back scattered image of the square in a. c SEM image of No. 3 with 0.6 wt% GNPs. d The corresponding magnification back scattered image of the square in c. e SEM image and X-ray mapping of No. 3 with 0.6 wt% GNPs: f Mg, g Al, h C

Fig. 4 a SEM image of No. 5 with 0.6 wt% GNPs after process adjustment. b and c Magnification images of the rectangular regions corresponding to a and b, respectively. The corresponding EDS analysis for point A is shown in the insets of b. The corresponding back scattered SEM image is shown in the insets of c. d X-ray mapping of Mg, Al, O, C for c

Fig. 5 Nyquist diagram of GNPs/Mg composites in SBF. Schematic diagram of equivalent circuit is shown in the inset

Fig. 6 Mass loss of GNPs/Mg composites. △m is average mass loss, and t is soak time

Fig.7 SEM images of GNPs/Mg composites after 1 h corrosion: a No. 1, b No. 2, c No. 3, d No. 4, e No. 5

Fig. 8 a SEM image of round dark area. The corresponding X-ray mapping: b Mg, c Al, d C, e Zn, f P, g Ca, h O

Fig. 9 a and i SEM images of the bright area. The corresponding X-ray mapping: b Mg, c Al, d Zn, e C, f P, g Ca, h O. j-l Corresponding EDS analysis for different points in i

Fig. 10 SEM images of the bright area with different GNPs contents: a No. 1, b No. 2, c No. 3, d No. 4

Fig. 11 SEM images of corrosion morphology comparison after parameter adjustment: a No. 1, b No. 5

Fig. 12 Phase-field simulated solute field evolution with different $\varphi_{0}$: a $\varphi_{0} = 2\pi$, c $\varphi_{0} = 2\pi \Delta t/500\Delta t$, $t_{{{\text{max}}}} = 50000\Delta t$. b and d Corresponding phase-field profiles at $t = 50000\Delta t$ with different $\varphi_{0}$