Departament de Química Analítica , Universitat de València , Dr. Moliner 50 , 46100 Burjassot , València , Spain.
Institut für Biochemie , Universität Greifswald , Felix-Hausdorff Straße 4 , 17487 Greifswald , Germany.
Acc Chem Res. 2019 Feb 19;52(2):400-406. doi: 10.1021/acs.accounts.8b00472. Epub 2019 Jan 7.
Dating needs an age-dependent phenomenon (a "clock"), a procedure for monitoring the advance of time by measuring a physicochemical quantity, and, in the case of archeological artifacts, a sampling procedure that guarantees the representativity and integrity of the dated objects. Metal corrosion in an aerobic atmosphere is a phenomenon whose advance can in principle be used as a clock that depends on the environmental conditions. In spite of the limitation imposed by differences in local conditions of corrosion, a new approach for age determinations has been developed and applied as a feasible tool for age determinations of metallic specimens studied by archeologists and historians. These techniques allow the recording of specific electrochemical features characterizing the state of growth of corrosion patinas, i.e., they are based on corrosion clocks. The application of corrosion clocks for age determination is possible in favorable cases where the corrosion happened to proceed uniformly and continuously. The proposed methods for dating of lead, copper/bronze, leaded bronze, and gold are mainly based on the voltammetry of immobilized particles (VIMP). This technique is exceptionally useful in the archeological domain because it requires only submicrogram sample amounts and permits sampling of different locations on the object, thus yielding representative data collected essentially noninvasively. Reported methods for dating of metals include lead, copper/bronze, and gold, obviously in all cases assuming uniform conditions of corrosion in a moderately aggressive environment. In the case of lead, age markers are porous PbO and PbO formed in the secondary patina. In the case of copper/bronze, aging is accompanied by a rise in the tenorite-to-cuprite ratio in the secondary patina. These changes in the composition of the patina can be monitored electrochemically using VIMP. The case of gold is different, as no "true" corrosion patina is formed. Here the age marker is the increase in electrochemically active gold sites, which is ultimately related to the adsorption of oxygen species and its diffusion/interchange/spillover through the external layers of the metal surface. Conjointly considered, such methods provide a new research line intersecting electrochemistry and cultural heritage that can be expanded via improvements in calibration and analysis to become an operative tool in the archeological domain.
年代测定需要一个与年龄相关的现象（“时钟”），一个通过测量物理化学量来监测时间流逝的程序，以及在考古文物的情况下，一个保证被测定对象具有代表性和完整性的采样程序。有氧气氛中的金属腐蚀是一种可以原则上用作取决于环境条件的时钟的现象。尽管由于腐蚀的局部条件差异而存在限制，但已经开发并应用了一种新的年代测定方法，作为考古学家和历史学家研究的金属标本年代测定的可行工具。这些技术允许记录表征腐蚀皮膜生长状态的特定电化学特征，即，它们基于腐蚀时钟。在腐蚀均匀连续进行的有利情况下，使用腐蚀时钟进行年龄测定是可能的。用于测定铅、铜/青铜、铅青铜和金的方法主要基于固定颗粒的伏安法（VIMP）。由于该技术仅需要亚微克样品量并且允许对物体的不同位置进行采样，因此可以非侵入性地收集代表性数据，因此在考古领域非常有用。报告的金属年代测定方法包括铅、铜/青铜和金，显然在所有情况下都假设在适度腐蚀性环境中腐蚀条件均匀。在铅的情况下，年龄标记物是次生皮膜中形成的多孔 PbO 和 PbO。在铜/青铜的情况下，老化伴随着次生皮膜中黑铜矿与赤铜矿的比例上升。可以使用 VIMP 电化学监测皮膜成分的这些变化。金的情况不同，因为没有形成“真正的”腐蚀皮膜。在这里，年龄标记物是电化学活性金位点的增加，这最终与氧物种的吸附及其通过金属表面的外部层的扩散/交换/溢出有关。综合考虑，这些方法提供了一条新的研究路线，将电化学与文化遗产相交，通过改进校准和分析，该方法可以扩展成为考古领域的一种可行工具。
