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. 2024 Apr 10;17(8):1734.
doi: 10.3390/ma17081734.

Microstructure and Chlorine Ion Corrosion Performance in Bronze Earring Relics

Zhiqiang Song  1   2 , Ojiyed Tegus  1   2
Affiliations

Microstructure and Chlorine Ion Corrosion Performance in Bronze Earring Relics

Zhiqiang Song et al. Materials (Basel). .

Abstract

Chlorine ions play an important role in the corrosion of bronzeware. This study employs techniques such as XRD, OM, SEM, EBSD, and electrochemical testing to analyze the microstructure, crystal structure, chemical composition, and corrosion performance of bronze earrings unearthed at the Xindianzi site in Inner Mongolia. The results indicate the presence of work-hardened structures, including twinning and equiaxed crystals, on the earrings' surface. With an increase in chloride ion concentration in NaCl solutions from 10-3 mol/L to 1 mol/L, the corrosion current density of the bronze earrings increased from 2.372 × 10-7 A/cm2 to 9.051 × 10-7 A/cm2, demonstrating that the alloy's corrosion rate escalates with chloride ion concentration. A 3-day immersion test in 0.5% NaCl solution showed the formation of a passivation layer of metal oxides on the earrings' surface. These findings underscore the significance of the impact chloride ions have on the corrosion of copper alloys, suggesting that activating the alloy's reactive responses can accelerate the corrosion process and provide essential insights into the corrosion mechanisms of bronze artifacts in chloride-containing environments.

Keywords: NaCl solution; alloy structure; bronze earrings; electrochemical corrosion; polarization curve.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Schematic depiction of the location of the Xindianzi Cemetery during the Eastern Zhou Dynasty.
Figure 2
Figure 2
(a) Bronze earring sampling and (b) coordinate system.
Figure 3
Figure 3
XRD pattern of bronze earrings.
Figure 4
Figure 4
Optical micrograph image of the bronze earring.
Figure 5
Figure 5
EBSD orientation map of the X-Y section of the bronze earring.
Figure 6
Figure 6
Polar diagram of the cross-section of the bronze earring.
Figure 7
Figure 7
Microstructural characteristics of bronze earrings: (a) map of grain size analysis and (b) map of orientation difference distribution.
Figure 8
Figure 8
EBSD characterization of the bronze earring: (a) Local orientation and (b) KAM map.
Figure 9
Figure 9
SEM-EDS and Cu, Sn, Pb elements distribution Map of bronze earrings (Cu78.36%, Sn10.71%, Pb10.82%).
Figure 10
Figure 10
Phase distribution map of the local area of the bronze earring by EBSD.
Figure 11
Figure 11
(a) SEM-EDS of Bronze Earrings and (b) the distribution of Cu and O Element Lines.
Figure 12
Figure 12
SEM-EDS images and elemental energy spectra of the bronze earrings before immersion (a,c) and after immersion for 3 days in 0.5 mol/L NaCl solution (b,d–f).
Figure 13
Figure 13
XRD pattern of copper–tin–lead alloy soaked in 0.5 mol/L NaCl solution for 3 days.
Figure 14
Figure 14
OCP curves of bronze earrings in NaCl solutions.
Figure 15
Figure 15
Tafel curves of bronze earrings in NaCl solutions.
Figure 16
Figure 16
(a) Nyquist plot and (b,c) Bode of bronze earrings in NaCl solutions.
Figure 17
Figure 17
(a) Nyquist plot and (b,c) Bode of bronze earrings after immersion for different times in 0.5 mol/L NaCl solution.
Figure 18
Figure 18
Equivalent circuits show the bronze earrings soaked in 0.5 mol/L NaCl initially (a) and for 3 days (b) [34].
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