Improved corrosion resistance of 5XXX aluminum alloy by homogenization heat treatment

In Kyu Choi; Soo Ho Cho; Sung Joon Kim; Yoo Shin Jo; Sang Ho Kim

doi:10.3390/coatings8010039

Improved corrosion resistance of 5XXX aluminum alloy by homogenization heat treatment

In Kyu Choi, Soo Ho Cho, Sung Joon Kim, Yoo Shin Jo, Sang Ho Kim

Research output: Contribution to journal › Article › peer-review

17 Scopus citations

Abstract

The corrosion resistance of homogenized Al-Mg (6.5%) alloy-adding Si, Zn, Mn, and Fe (0.2%) to improve various properties-was observed. Differential scanning calorimetry (DSC) and a JMatPro simulation revealed that the optimal homogenization temperature was 450 °C. The homogenization was carried out at 450 °C for 3, 6, 12, 18, 24, and 30 h in order to view the corrosion resistance change. Corrosion resistance was analyzed by a polarization test in 3.5 wt % NaCl solution. The corrosion resistance improved with increasing homogenization time up to 24 h, but there was no change with longer time periods. To observe the reason for the change in corrosion resistance, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDS) analyses were performed. Precipitates containing Mg, such as Al₃Mg₂ and Mg₃₂(Al, Zn)₄₉, decreased at the grain boundary. After homogenization, the amount of Mg measured by SEM-EDS at the grain boundary decreased from 36% to 8%, while Si increased. Generally, the potential difference between the grain boundary and the grains leads to intergranular corrosion. Reduction of Mg, whose standard electrode potential is lower than that of Al, and an increase of Si, which is present in higher concentration than Al at the grain boundaries, improved the corrosion resistance of 5XXX Al alloy by reducing the intergranular corrosion.

Original language	English
Article number	39
Journal	Coatings
Volume	8
Issue number	1
DOIs	https://doi.org/10.3390/coatings8010039
State	Published - Jan 1 2018
Externally published	Yes

Funding

4.ConclusionsIn this study, a newAl-Mg-Zn-Mn-Fe-Si Al 5XXX alloy was homogenized and the corrosion resistance was investigated. Homogenization was conducted at 450 °C for 3, 6, 12, 18, 24, and 30 h. The corrosion resistance improved steadily with homogenization ◦time and saturated after 24 h. With homogenization, the grain boundary volume fraction decreased and the corrosion rate decreased. The corrosion resistance improved steadily with homogenization time and saturated after 24 h. The second phases recognized at the grain boundary are mainly β(Al3Mg2), τ(Mg32(Al, Zn)49), and With homogenization, the grain boundary volume fraction decreased and the corrosion rate decreased. Al6(Mn, Fe) before homogenization and Mg2Si and Si after homogenization. The secondThe secondphasesary phase prrecognizedesent in theat the graingrain bounboundarydary hare mainlyad a larβg(Ale amoun3Mg2),tτof Mg before(Mg32(Al, Zn)49), ho6mogenization and it is thought that the Mg2, wtih a lower standard reduction potential, would The secondary phase present in the grain boundary had a large amount of Mg before homogenWiziathti ohnomaongdenziitatiiosnt, hthoeuβ gahntdt τhpahtastheewiMthg h,igwh iMtghcoanltoenwte drercsetaasneddaa rtd threeg drauicnt iboonundpaortyential, by diffusion into grains, while Si preferentially diffused to the grain boundary at high temperature homogenization can remain in Si and/or Mg2Si at the grain boundary. Furthermore, the high reduction potential of Si and sacrificial Mg2Si would reduce the intergranular corrosion, resulting in the better corrosion resistance of the newly developed Al 5XXX alloy. homogenizationcanremaininSiand/orMg2Si at the grain boundary. Furthermore, the high reduction potential of Si and sacrificial Mg Si would reduce the intergranular corrosion, resulting in the better corrosion resistance of the newly developed Al 5XXX alloy. Author Contributions: Sang-Ho Kim and In-Kyu Choi conceived and designed the experiments; In-Kyu Choi performed the experiments; In-Kyu Choi, Soo-Ho Cho, Sung-Joon Kim, and Yoo-Shin Jo analyzed the data; Acknowledgments: This work was financially supported by the Korea University of Technology and Education. In-Kyu Choi, Soo-Ho Cho, Sung-Joon Kim, and Yoo-Shin Jo contributed reagents/materials/analysis tools; AuthSoarnCgo-nHtori Kbuimti onands I:nS-Kanygu- HChooKi iwmroatned thIpnea-pKeyru. Choi conceived and designed the experiments; In-Kyu Choi performed the experiments; In-Kyu Choi, Soo-Ho Cho, Sung-Joon Kim, and Yoo-Shin Jo analyzed the data; Conflicts of Interest: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. Conflicts of Interest: The authors declare no conflict of interest. The founding sponsors had no role in the design

Funders	Funder number
Korea University of Technology and Education

Keywords

Aluminum alloy
Corrosion resistance
Homogenization
Polarization test

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10.3390/coatings8010039

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title = "Improved corrosion resistance of 5XXX aluminum alloy by homogenization heat treatment",

abstract = "The corrosion resistance of homogenized Al-Mg (6.5%) alloy-adding Si, Zn, Mn, and Fe (0.2%) to improve various properties-was observed. Differential scanning calorimetry (DSC) and a JMatPro simulation revealed that the optimal homogenization temperature was 450 °C. The homogenization was carried out at 450 °C for 3, 6, 12, 18, 24, and 30 h in order to view the corrosion resistance change. Corrosion resistance was analyzed by a polarization test in 3.5 wt % NaCl solution. The corrosion resistance improved with increasing homogenization time up to 24 h, but there was no change with longer time periods. To observe the reason for the change in corrosion resistance, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDS) analyses were performed. Precipitates containing Mg, such as Al3Mg2 and Mg32(Al, Zn)49, decreased at the grain boundary. After homogenization, the amount of Mg measured by SEM-EDS at the grain boundary decreased from 36% to 8%, while Si increased. Generally, the potential difference between the grain boundary and the grains leads to intergranular corrosion. Reduction of Mg, whose standard electrode potential is lower than that of Al, and an increase of Si, which is present in higher concentration than Al at the grain boundaries, improved the corrosion resistance of 5XXX Al alloy by reducing the intergranular corrosion.",

keywords = "Aluminum alloy, Corrosion resistance, Homogenization, Polarization test",

author = "Choi, {In Kyu} and Cho, {Soo Ho} and Kim, {Sung Joon} and Jo, {Yoo Shin} and Kim, {Sang Ho}",

note = "Publisher Copyright: {\textcopyright} 2018 by the authors.",

year = "2018",

month = jan,

day = "1",

doi = "10.3390/coatings8010039",

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volume = "8",

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T1 - Improved corrosion resistance of 5XXX aluminum alloy by homogenization heat treatment

AU - Choi, In Kyu

AU - Cho, Soo Ho

AU - Kim, Sung Joon

AU - Jo, Yoo Shin

AU - Kim, Sang Ho

PY - 2018/1/1

Y1 - 2018/1/1

N2 - The corrosion resistance of homogenized Al-Mg (6.5%) alloy-adding Si, Zn, Mn, and Fe (0.2%) to improve various properties-was observed. Differential scanning calorimetry (DSC) and a JMatPro simulation revealed that the optimal homogenization temperature was 450 °C. The homogenization was carried out at 450 °C for 3, 6, 12, 18, 24, and 30 h in order to view the corrosion resistance change. Corrosion resistance was analyzed by a polarization test in 3.5 wt % NaCl solution. The corrosion resistance improved with increasing homogenization time up to 24 h, but there was no change with longer time periods. To observe the reason for the change in corrosion resistance, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDS) analyses were performed. Precipitates containing Mg, such as Al3Mg2 and Mg32(Al, Zn)49, decreased at the grain boundary. After homogenization, the amount of Mg measured by SEM-EDS at the grain boundary decreased from 36% to 8%, while Si increased. Generally, the potential difference between the grain boundary and the grains leads to intergranular corrosion. Reduction of Mg, whose standard electrode potential is lower than that of Al, and an increase of Si, which is present in higher concentration than Al at the grain boundaries, improved the corrosion resistance of 5XXX Al alloy by reducing the intergranular corrosion.

AB - The corrosion resistance of homogenized Al-Mg (6.5%) alloy-adding Si, Zn, Mn, and Fe (0.2%) to improve various properties-was observed. Differential scanning calorimetry (DSC) and a JMatPro simulation revealed that the optimal homogenization temperature was 450 °C. The homogenization was carried out at 450 °C for 3, 6, 12, 18, 24, and 30 h in order to view the corrosion resistance change. Corrosion resistance was analyzed by a polarization test in 3.5 wt % NaCl solution. The corrosion resistance improved with increasing homogenization time up to 24 h, but there was no change with longer time periods. To observe the reason for the change in corrosion resistance, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDS) analyses were performed. Precipitates containing Mg, such as Al3Mg2 and Mg32(Al, Zn)49, decreased at the grain boundary. After homogenization, the amount of Mg measured by SEM-EDS at the grain boundary decreased from 36% to 8%, while Si increased. Generally, the potential difference between the grain boundary and the grains leads to intergranular corrosion. Reduction of Mg, whose standard electrode potential is lower than that of Al, and an increase of Si, which is present in higher concentration than Al at the grain boundaries, improved the corrosion resistance of 5XXX Al alloy by reducing the intergranular corrosion.

KW - Aluminum alloy

KW - Corrosion resistance

KW - Homogenization

KW - Polarization test

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VL - 8

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ER -

Improved corrosion resistance of 5XXX aluminum alloy by homogenization heat treatment

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