综述了甲酸、乙酸对馆藏铜质文物的腐蚀机理和产物,涉及对铜基体的腐蚀、对已有氯化物锈蚀产物的铜的腐蚀以及对表面有碱性Na、K化合物的铜质文物的腐蚀.有机酸对表面有无碱性Na、K化合物的铜的腐蚀有着截然不同的机理和产物.当无Na、K化合物时,产物包括Cu(HCOO)2、Cu(OH)(HCOO)、Cu(OH)2、Cu(CH3COO)2 和 Cu4(OH)(CH3COO)7·2H2O;而存在碱性 Na 化合物时,主要产物为 Cu4Na4O(HCOO)8(H2O)4(OH)2、Cu2(OH)3(HCOO)和NaCu(CO3)(CH3COO).近年来,国内外发现了大量相关文物腐蚀的案例,腐蚀产物主要是后者,表明了碱性Na、K化合物和有机酸在腐蚀中的作用.Na、K化合物的来源包括文物在铸造、使用、埋藏和保护修复过程中引入以及复合材质文物中的其他材质(如玻璃或珐琅),有机酸则主要来源于保存展览环境中的木材、板材、涂料、粘合剂等的挥发或降解.
A Review of the Corrosion of Copper-Based Artifacts in Museum Collections by Organic Acids
The corrosion mechanisms and products of copper-based artifacts in museum collections induced by formic acid and acetic acid are reviewed.It encompasses corrosion of the copper substrate,corrosion with chloride-products,and corrosion of copper-based artifacts containing alkaline Na and K compounds.Organic acids exhibit significantly different corrosion mechanisms and products depending on the presence of alkaline Na and K compounds.In the absence of Na and K compounds,the products include Cu(HCOO)2,Cu(OH)(HCOO),Cu(OH)2,Cu(CH3COO)2·2H2O,and Cu4(OH)(CH3COO)7·2H2O;whereas in the presence of alkaline Na compounds,the main products are Cu4Na4O(HCOO)8(H2O)4(OH)2,Cu2(OH)3(HCOO),and NaCu(CO3)(CH3COO).Numerous cases of copper-based artifacts corrosion by organic acids have been discovered globally in recent years,primarily yielding the latter products,which underscores the role of alkaline Na and K compounds and organic acids in corrosion.Sources of Na and K compounds include their introduction during casting,use,burial,and conservation-restoration processes of artifacts,as well as other materials in composite artifacts(such as glass or enamel),and the organic acids mainly originate from the volatilization or degradation of materials like wood,boards,paint,and adhesives in the storage and exhibition environment.
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