Intensification of Electrochemical Performance of AA7075 Aluminum Alloys Using Rare Earth Functionalized Water-Based Polymer Coatings
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
2.2. Synthesis and Deposition of Hybrid Coatings
2.3. Characterizaction of Samples
2.4. Electrochemical Characterization
2.5. Salt Spray Test
3. Results and Discussion
3.1. Structural and Optical Characterizations
3.2. Electrochemical Performance
3.3. Salt Spray Chamber
4. Conclusions
- -
- Ceria nanoparticles dispersion in WPU follows the typical dispersion mechanism, where agglomeration can be avoided or minimized using the sonication approach.
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- The excess of water in the reaction medium provokes important changes in the coating porosity that compromises its performance in terms of aggressive species diffusion through the WPU–CeO2/AA7075 systems.
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- The fcc structure that remains after WPU polymerization indicates that CeO2 nanostructures are unaffected during their incorporation into the polymeric matrix, although the amount of nanostructures and sonication time significantly affect the average crystallite size (from 8.2 to 27.7 nm) and orientation onto the metallic substrates.
- -
- The texture of CeO2 can be modulated with the synthesis parameters as well as affect the physical integration to the polymer matrix.
- -
- The nanoceria amount and sonication time during the synthesis play a crucial role in enhancing the optical transparence of WPUs, which helps to delay yellowing.
- -
- The electrochemical performance of the samples indicates that 1 wt % of CeO2 nanostructures is insufficient for a homogeneous incorporation to the polymers to seal pores while excessive nanostructures (e.g., 5 wt %) provoke agglomeration and coalescence in the polymer matrix.
- -
- An optimal electrochemical performance is achieved with 3 wt % of CeO2 (30 min) nanoparticles, highlighting the importance of both ceria content and sonication time, as synthesis parameters.
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- Hybrid coatings with optimal conditions displayed impedance values up to four orders of magnitude higher than that obtained for pure WPU on metallic substrate, which were in agreement with salt fog exposure tests.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Element | Si | Fe | Cu | Mn | Zn | Ti | Cr | Mg | Al |
---|---|---|---|---|---|---|---|---|---|
Weight % | 0.137 | 0.262 | 1.629 | 0.062 | 5.36 | 0.045 | 0.20 | 2.26 | balance |
Coating on AA7075 | Crystallite size (nm) |
---|---|
WPU–CeO2, 30 min (3 wt %) | 25.2 |
WPU–CeO2, 30 min (5 wt %) | 27.7 |
WPU–CeO2, 60 min (3 wt %) | 8.9 |
WPU–CeO2, 60 min (5 wt %) | 8.2 |
WPU–CeO2, 120 min (3 wt %) | 8.5 |
WPU–CeO2, 120 min (5 wt%) | 22.4 |
Sample | Eocp (V vs. SCE) | ||||
---|---|---|---|---|---|
C1 | C6 | C12 | C18 | C24 | |
AA7075 | −0.73 ± 0.01 | −0.72 ± 0.01 | −0.77 ± 0.03 | −0.78 ± 0.03 | −0.74 ± 0.05 |
PU | −0.80 ± 0.15 | −0.80 ± 0.12 | −0.76 ± 0.12 | −0.84 ± 0.06 | −0.82 ± 0.05 |
PU–CeO2, 30 min (1 wt %) | −0.79 ± 0.1 | −0.81 ± 0.09 | −0.88 ± 0.09 | −0.88 ± 0.08 | −0.87 ± 0.11 |
PU–CeO2 30 min (3 wt %) | −1.92 ± 0.78 | −0.87 ± 0.2 | −0.67 ± 0.01 | −0.66 ± 0.04 | −0.65 ± 0.07 |
PU–CeO2 30 min (5 wt %) | −0.56 ± 0.12 | −0.82 ± 0.1 | −0.85 ± 0.06 | −0.87 ± 0.06 | −0.9 ± 0.08 |
PU–CeO2 60 min (1 wt %) | −0.72 ± 0.02 | −0.75 ± 0.04 | −0.75 ± 0.03 | −0.79 ± 0.07 | −0.77 ± 0.02 |
PU–CeO2 60 min (3 wt %) | −0.74 ± 0.07 | −0.74 ± 0.04 | −0.76 ± 0.02 | −0.8 ± 0.07 | −0.82 ± 0.08 |
PU–CeO2 60 min (5 wt %) | −0.67 ± 0.06 | −0.65 ± 0.11 | −0.77 ± 0.06 | −0.78 ± 0.05 | −0.78 ± 0.04 |
PU–CeO2 120 min (1 wt %) | −0.46 ± 0.01 | −0.71 ± 0.02 | −0.85 ± 0.02 | −0.88 ± 0.02 | −0.86 ± 0.02 |
PU–CeO2 120 min (3 wt %) | −0.63 ± 0.02 | −0.63 ± 0.01 | −0.66 ± 0.01 | −0.66 ± 0.02 | −0.72 ± 0.02 |
PU–CeO2 120 min (5 wt %) | −0.69 ± 0.04 | −0.71 ± 0.06 | −0.74 ± 0.02 | −0.76 ± 0.02 | −0.77 ± 0.01 |
Sample | Rs (Ω cm2) | Rcoat (Ω cm2) | Rct (Ω cm2) | Y0coat (S*sn) | ncoat | Y0dl (S*sn) | ntc | W (S*s1/2) | χ2 | |
---|---|---|---|---|---|---|---|---|---|---|
AA7075 | 21.3 | 6.80 × 103 | 2.24 × 104 | 2.28×10−5 | 0.91 | 3.65 × 10−4 | 0.77 | --- | 1.81 × 10−3 | |
WPU | 19.7 | 2.19 × 105 | 7.52 × 104 | 1.84 × 10−6 | 0.75 | 1.05 × 10−9 | 0.90 | 8.218 | 1.52 × 10−5 | |
WPU–CeO2, 120 min (1 wt %) | 45.2 | 2.35 × 107 | 3.75 × 107 | 2.73 × 10−10 | 0.97 | 3.17 × 10−8 | 0.76 | --- | 1.8 × 10−2 | |
WPU–CeO2, 30 min (3 wt %) | 30.1 | 2.25 × 109 | 6.10 × 109 | 1.32 × 10−10 | 0.96 | 2.24 × 10−9 | 0.71 | --- | 2.3 × 10−2 | |
WPU–CeO2, 30 min (5 wt %) | 50.6 | 9.32 × 106 | 3.60 × 107 | 9.47 × 10−10 | 0.87 | 6.93 × 10−8 | 0.62 | --- | 1.1 × 10−2 |
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Ferrel-Álvarez, A.C.; Domínguez-Crespo, M.A.; Torres-Huerta, A.M.; Cong, H.; Brachetti-Sibaja, S.B.; López-Oyama, A.B. Intensification of Electrochemical Performance of AA7075 Aluminum Alloys Using Rare Earth Functionalized Water-Based Polymer Coatings. Polymers 2017, 9, 178. https://doi.org/10.3390/polym9050178
Ferrel-Álvarez AC, Domínguez-Crespo MA, Torres-Huerta AM, Cong H, Brachetti-Sibaja SB, López-Oyama AB. Intensification of Electrochemical Performance of AA7075 Aluminum Alloys Using Rare Earth Functionalized Water-Based Polymer Coatings. Polymers. 2017; 9(5):178. https://doi.org/10.3390/polym9050178
Chicago/Turabian StyleFerrel-Álvarez, Atzin C., Miguel A. Domínguez-Crespo, Aidé M. Torres-Huerta, Hongbo Cong, Silvia B. Brachetti-Sibaja, and Ana B. López-Oyama. 2017. "Intensification of Electrochemical Performance of AA7075 Aluminum Alloys Using Rare Earth Functionalized Water-Based Polymer Coatings" Polymers 9, no. 5: 178. https://doi.org/10.3390/polym9050178