| ZOU An,DENG Yun-lai,YE Ling-ying,GUO Xiao-bin.Correlation between Localized Corrosion and Electrochemical Performance of 7050 Aluminum Alloy[J],51(10):226-234 |
| Correlation between Localized Corrosion and Electrochemical Performance of 7050 Aluminum Alloy |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.10.023 |
| KeyWord:Al7Cu2Fe phase 7050 aluminum alloy in-situ corrosion electrochemistry |
| Author | Institution |
| ZOU An |
School of Materials Science and Engineering, Central South University, Changsha , China |
| DENG Yun-lai |
School of Materials Science and Engineering, Central South University, Changsha , China |
| YE Ling-ying |
School of Materials Science and Engineering, Central South University, Changsha , China |
| GUO Xiao-bin |
School of Materials Science and Engineering, Central South University, Changsha , China |
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| Abstract: |
| In order to explore the pitting corrosion mechanism of 7050 aluminum alloy and the influence of Al7Cu2Fe on the corrosion performance of 7050 aluminum alloy. In this paper, ZEISSM10A scanning electron microscope (SEM) and energy spectrometer (EDS) were used to analyze the Al7Cu2Fe phase on the surface of 7050 aluminum alloy samples corroded in NaCl solution for different time. Combined with the corresponding electrochemical impedance spectroscopy, the influence of the difference of Al7Cu2Fe phase composition and size on the corrosion performance of 7050 aluminum alloy was studied. The study found that the specific composition of the AlxCuyFe phase on the surface of the T6 7050 aluminum alloy is in the range of Al60.3Cu2.7Fe to Al7.4Cu2Fe, so the second phase of the Al7Cu2Fe type is studied in this paper. And with the increase of the size of the Al7Cu2Fe phase, its Fe content tends to increase overall. Among them, the Al7Cu2Fe phase with the size in the range of 1.5-3 μm has the largest number and the largest area, accounting for 79.1% of the total Al7Cu2Fe phase area. The in-situ corrosion results show that the pitting characteristics of the AlxCuyFe phase depend on the size and composition of the phase, and the change rate of Fe content in the AlxCuyFe phase first increases and then decreases. Among them, the largest change in Fe content is the Al7Cu2Fe phase with an average diameter of about 1.7 μm. After 1.5 h of corrosion, the change rate reaches 58.62%. Secondly, the Al7Cu2Fe phase with an average diameter of about 2.4 μm has a change rate of 52.13% after 1 h of corrosion, while the Fe content change rate of the Al7Cu2Fe phase with an average diameter of about 2.4 μm during the pitting corrosion process is mostly below 10%. The results of electrochemical impedance spectroscopy showed that the Rs value of the samples after different corrosion treatments changed greatly. The Rs value of the sample after corrosion for 0.5 h was the highest, reaching 29.84 Ω, and the Rs value of the sample after corrosion for 1.5 h was the lowest, which was 2.20 Ω. The resistance of 7050 aluminum alloy in T6 state after being immersed and corroded in a NaCl solution with a concentration of 150 g/L decreases first and then increases. After 2 h of corrosion, the resistance is the strongest, with Rp value of 229.3 Ω and Rb value it is 2 801 Ω. Therefore, we can find that the surface pitting corrosion of 7050 aluminum alloy in T6 state in 150 g/L NaCl solution mainly occurs within 0.5 h to 1.5 h, and the alloy is not affected by surface pitting corrosion caused by Al7Cu2Fe phase after 2 h corrosion. When the immersion time reaches 2 h, the size and Fe content of the Al7Cu2Fe phase are slightly reduced. Compared with the uncorroded state, the overall area of the Al7Cu2Fe phase is reduced by 4.72%, and the Fe content is reduced by 7.59%. The Al7Cu2Fe phase with an average diameter in the range of 1.5-2.5 μm has a greater influence on the Rb value. In summary, the main influence on the pitting corrosion performance of 7050 alloy is the AlxCuyFe phase with a size range of 1.5-2.5 μm. The Fe content and size change during the corrosion process are more significant than those in the size range of 2.5-9.5 μm. |
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