Abstract
In general, during long-term museum conservation, ancient bronzes will generate new corrosion products also called the “secondary corrosion” on the surface of the unearthed “primary corrosion” products due to various environmental conditions. In this paper, the corrosion stages of several ancient Chinese bronzes are characterized by using optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman spectrometer (Raman). It is found that there exist phase transformation relationships in between the “primary corrosion” and the “secondary corrosion” stages (i.e., (1) the crystal lattice type tends to transform from a high symmetry system to a low symmetry system; (2) in case of the same crystal lattice type, the corrosions exhibit an inter-transformation or symbiosis). It is interesting to note that these transformation rules are very consistent with the well-known physical law of “spontaneous symmetry-breaking”, which won the 2008 Nobel Prize in Physics and also has been considered to be general law of nature, in addition to the principle of Gibbs free energy reduction. The significance of this discovery allows us to achieve the predictability and controllability of the bronze corrosion products (i.e., to predict the corrosive trends in advance and control the “second corrosion” by adjusting the conservation conditions. This research provides a novel conservation concept of ancient bronzes.
Highlights
Ancient Chinese bronzes are the treasures of Chinese cultural relics, which mostly represent the splendid bronze civilization of the dynasties Xia, Shang and Zhou from 2070 BC to 221 BC.Throughout several millennia of soil burial or conservation in variant environmental conditions, different corrosion products are generated
Harmful corrosion appears in the form of a white-green powder, called the “powdery corrosion” or “bronze disease” [2], which consists of the reactive cuprous chloride (CuCl) species and Minerals 2020, 10, 656; doi:10.3390/min10080656
We introduce a novel discovery that the relationship between the ancient bronze’s “primary corrosion” and “secondary corrosion” agrees with the law of “spontaneous symmetry-breaking”
Summary
Throughout several millennia of soil burial or conservation in variant environmental conditions, different corrosion products are generated. These corrosion products can be divided into two sorts (i.e., harmless and harmful to the bronzes [1]). Harmless corrosion refers to a process in which the corrosion products will not further penetrate into the bronze body during conservation. Harmful corrosion appears in the form of a white-green powder, called the “powdery corrosion” or “bronze disease” [2], which consists of the reactive cuprous chloride (CuCl) species and Minerals 2020, 10, 656; doi:10.3390/min10080656 www.mdpi.com/journal/minerals. Minerals 2020, 10, 656 can further form the greenish 2Cu2 (OH) Cl (atacamite and its polymorphs) in humid environments continuously, and damage the whole bronzes [3]. The harmful products must be properly treated as early as possible, and many researchers have engaged in this study for many years
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