青銅病：考古銅基錢幣保護的主要挑戰

腐蝕反應是博物館室內環境、室外大氣、埋土等各種環境中影響金屬遺產的主要危害現象。硬幣是具有內在價值的小物體，包含與當時的建築、文化和藝術相關的資訊。

Corrosion is a major threat to metal artifacts in various environments, including museums, outdoor atmosphere, and burial soil. Coins, being small objects with intrinsic value, hold rich information about architecture, culture, and arts of their time. They often bear images of rulers, national or religious symbols, and inscriptions, offering insights into the political and economic history of their period. Many coins show important buildings, temples, and other architectural marvels, serving as small canvases for the artistic styles of their period. The study of coins combines elements of history, archaeology, and art history.

腐蝕是各種環境中金屬文物的主要威脅，包括博物館、室外大氣和埋土。錢幣是具有內在價值的小物件，蘊藏著有關當時建築、文化和藝術的豐富資訊。它們通常帶有統治者的圖像、國家或宗教象徵以及銘文，讓人們深入了解該時期的政治和經濟歷史。許多硬幣都描繪了重要的建築物、寺廟和其他建築奇蹟，充當了當時藝術風格的小畫布。硬幣的研究結合了歷史、考古學和藝術史的元素。

Bronze represents a class of alloys widely used in ancient times, valued for its hardness and greater corrosion-resistant compared to pure metals. Ancient cast bronze typically contains copper with varying amounts of tin, and zinc depending on the desired properties of the alloy. The addition of lead (Pb) improved the fluidity of molten bronze, making it a preferred material for production of decorative coins, particularly during the Greco-Roman ages. The corrosion products of bronze are mainly composed of copper oxides, forming a uniform pale brown to black-brown layer known as the primary patina. Preserving this patina especially the cuprite, along with surface details, is the main goal in the conservation of copper-based coins.

青銅代表了古代廣泛使用的一類合金，與純金屬相比，因其硬度和更高的耐腐蝕性而受到重視。古代鑄造青銅通常含有銅以及不同含量的錫和鋅，具體取決於合金的所需性能。添加鉛 (Pb) 改善了熔融青銅的流動性，使其成為生產裝飾硬幣的首選材料，特別是在希臘羅馬時代。青銅的腐蝕產物主要由銅氧化物組成，形成均勻的淺棕色至黑棕色層，稱為初生銅綠。保護銅鏽（尤其是赤銅礦）以及表面細節是保護銅基硬幣的主要目標。

Patina is a thin, natural or artificial layer that forms on bronze due to chemical reactions such as oxidation. It develops over time through exposure to environmental factors, including humidity, pollution, and soil. Patinas are composed of compounds such as copper oxides (e.g., cuprite), carbonates (e.g., malachite), or sulfates. Natural patinas provide protection against corrosion, while artificial patinas are applied for aesthetic or protective purpose. In archaeology, patinas are valuable as they act as a historical record and serve as a protective barrier, making their preservation crucial in conservation efforts.

銅綠是由於氧化等化學反應而在青銅上形成的一層薄薄的天然或人造層。隨著時間的推移，它會透過暴露於環境因素（包括濕度、污染和土壤）而發展。銅鏽由銅氧化物（例如赤銅礦）、碳酸鹽（例如孔雀石）或硫酸鹽等化合物組成。天然銅綠可提供防腐蝕保護，而人造銅綠則用於美觀或保護目的。在考古學中，銅綠很有價值，因為它們可以作為歷史記錄並充當保護屏障，使其保存對於保護工作至關重要。

Surface degradation occurs due to corrosion, which involves not only oxidation but also the formation of copper chlorides (bronze disease) and other corrosion products that vary in thickness and composition. Bronze disease is an active corrosion process in which bronze reacts with chloride ions to form cuprous chloride (CuCl), leading to metal degradation. In humid environments, cuprous chloride reacts with water to produce hydrochloric acid, further accelerating deterioration. This results in pitting and flaking, weakening the structural integrity of artifacts. Bronze disease can compromise the structural, historical, and aesthetic values of archaeological coins. The reaction speed on the bronze surface varies depending on the object’s history and surrounding environment.

表面退化是由於腐蝕而發生的，腐蝕不僅涉及氧化，還涉及氯化銅（青銅病）和其他厚度和成分不同的腐蝕產物的形成。青銅病是一種活躍的腐蝕過程，其中青銅與氯離子反應形成氯化亞銅 (CuCl)，導致金屬降解。在潮濕的環境中，氯化亞銅與水反應生成鹽酸，進一步加速變質。這會導致凹坑和剝落，削弱文物的結構完整性。青銅病會損害考古錢幣的結構、歷史和美學價值。青銅表面的反應速度會根據物體的歷史和周圍環境而變化。

Sulfur and chloride ions can penetrate the patina and metal core, causing pits to form on the surface. Aggressive chloride accelerates the dissolution of copper-based alloys, causing the loss of native protective layers in burial environments. The corrosion layers mainly consist of malachite (CuCO3. Cu(OH)2), which disrupts the CuCl/Cu2O mixture and causes exfoliation. Post-excavation cuprous chloride (CuCl) hydrolyzes into hydroxyl chloride polymorphs Cu2OH3Cl in the presence of water. Bronze disease occurs with the formation polymorphous copper hydroxyl chlorides, including atacamite, paratacamite, clinoatacamite, and botallackite.

硫和氯離子可以滲透銅綠和金屬芯，導致表面形成凹坑。侵蝕性氯化物會加速銅基合金的溶解，導致埋藏環境中天然保護層的喪失。腐蝕層主要由孔雀石 (CuCO3.Cu(OH)2) 組成，它會破壞 CuCl/Cu2O 混合物並導致剝落。開挖後的氯化亞銅 (CuCl) 在水存在下水解成羥基氯化物多晶型 Cu2OH3Cl。青銅病隨著多晶型羥基氯化銅的形成而發生，包括氯銅礦、副氯銅礦、斜氯銅礦和斜氯銅礦。

Lead plays an effective role in influencing the corrosion rate by forming highly stable lead carbonates and insoluble lead chloride, which remain stable after excavation. Protective conservation is the most effective process to prevent or at least delay degradation. However, achieving suitable environmental conditions is challenging, making it necessary to apply a protective system. Protective coatings, including natural patinas or applied treatments, inhibit corrosion by forming a barrier against moisture, oxygen, and pollutants, helping to preserve the artifact and minimize further damage. The coating system is a significant topic to stop corrosion and ensure the long-term stability of archaeological coins. There is a continuous study to provide better protection for objects by preventing the influence of humidity and contaminations with special requirements for conservation-restoration ethics such as ease of application, transparency, good appearance, long-term stability, reversibility, and safety for conservators-restorers and the environment.

鉛透過形成高度穩定的碳酸鉛和不溶性氯化鉛，在挖掘後保持穩定，從而有效影響腐蝕速率。保護性保存是防止或至少延緩退化的最有效過程。然而，實現合適的環境條件具有挑戰性，因此有必要應用保護系統。保護性塗層，包括天然銅鏽或應用處理，透過形成防潮、氧氣和污染物的屏障來抑制腐蝕，有助於保護文物並最大限度地減少進一步的損壞。塗層系統是防止腐蝕並確保考古錢幣長期穩定的重要課題。人們不斷進行研究，透過防止濕度和污染的影響來為物品提供更好的保護，並滿足保護修復倫理的特殊要求，例如易於使用、透明度、良好​​的外觀、長期穩定性、可逆性和保護者的安全性。

Through ancient conservation, natural resins were used to coat metal surfaces, but they often curled and flaked away. In contrast, methyl acrylate/ ethyl methacrylate 30:70% (Paraloid B-72®) is considered the most widely used coating for archaeological objects in Egypt due to its economic efficiency, transparency, and reversibility. It can be applied on both clean metal surfaces and those covered with patina.

透過古代的保護，天然樹脂被用來塗覆金屬表面，但它們經常捲曲和剝落。相較之下，丙烯酸甲酯/甲基丙烯酸乙酯 30:70% (Paraloid B-72®) 因其經濟效率、透明度和可逆性而被認為是埃及考古文物中使用最廣泛的塗層。它可以應用於乾淨的金屬表面和覆蓋有銅綠的表面。

The study of archeological coins is essential for both the preservation of cultural heritage and advancements in corrosion science. Analyzing the corrosion products of bronze archeological coins provides insights into the surface morphology, which aids in the preservation of cultural heritage.

考古硬幣的研究對於文化遺產的保護和腐蝕科學的進步至關重要。分析青銅考古錢幣的腐蝕產物可以深入了解表面形態，有助於保護文化遺產。