Corrosion and wear performance of La2O3 doped plasma electrolytic oxidation coating on pure Mg

Role of rare‐earth Y addition on formation and anticorrosion properties of MAO coating on 2024 aviation aluminum alloy

“…In the Bode plot, |Z| 0.01 Hz had important reference meaning, and its value could reflect the overall resistance magnitude of the coating, which in turn affected the overall barrier performance of the sample. 33 In Figure 8, it can be seen that the variation trend of |Z| 0.01 Hz for each sample after the addition of yttrium nitrate is consistent with the capacitive arc radius in the Nyquist plot, and the addition of yttrium nitrate at 1.5 g/L has the largest |Z| 0.01 Hz (5.63 × 10 5 Ω cm 2 ). Furthermore in the frequency-phase angle curves, it can be seen that each curve has two time constants, one in the high frequency range ( 10 there are at least two state variables corresponding to the whole frequency range.…”

“…In Figure 8, it can be seen that the variation trend of | Z | 0.01 Hz for each sample after the addition of yttrium nitrate is consistent with the capacitive arc radius in the Nyquist plot, and the addition of yttrium nitrate at 1.5 g/L has the largest | Z | 0.01 Hz (5.63 × 10 5 Ω cm 2 ). Furthermore in the frequency–phase angle curves, it can be seen that each curve has two time constants, one in the high frequency range (10 5 –10 4 Hz) and the other in the medium frequency range (10 2 –10 0 Hz), indicating that there are at least two state variables corresponding to the whole frequency range 33 …”

“…From the frequency‐impedance modulus curve, it can be seen that the impedance modulus continuously increases as the frequency decreases and stabilizes at .01 Hz. In the Bode plot, | Z | 0.01 Hz had important reference meaning, and its value could reflect the overall resistance magnitude of the coating, which in turn affected the overall barrier performance of the sample 33 . In Figure 8, it can be seen that the variation trend of | Z | 0.01 Hz for each sample after the addition of yttrium nitrate is consistent with the capacitive arc radius in the Nyquist plot, and the addition of yttrium nitrate at 1.5 g/L has the largest | Z | 0.01 Hz (5.63 × 10 5 Ω cm 2 ).…”

“…Furthermore in the frequency-phase angle curves, it can be seen that each curve has two time constants, one in the high frequency range ( 10 there are at least two state variables corresponding to the whole frequency range. 33 To further investigate the structure and reaction processes in each coating, equivalent circuit model was constructed to explain the coating structure of the relevant specimens, as shown in Figure 9. In the equivalent circuit, R s is the solution resistance of SSW, Q p and Q b are the nonideal capacitances corresponding to the outer porous layer and inner dense layer of the MAO coating, and R p and R b are the resistances corresponding to the porous layer and dense layer.…”

“…The yttrium oxide particles were then dissolved by the electrolyte and subsequently enter the discharge channel, where they were distributed along the discharge channel and its bottom, which contributed to enhance the denseness of the coating. 33 In addition, Y 2 O 3 can inhibit the growth of ceramic crystal, thereby refining the grains to enhance the denseness of the coating. 12 Therefore, the addition of Y(NO 3 ) 3 ⋅6H 2 O to the electrolyte could increase the thickness, hardness, and denseness of the coating.…”