Laser-Assisted Method for Cleaning and Analysis of Archaeological Metallic Coins

Abstract

Metal coins discovered during archaeology have artistic and cultural value. Careful cleaning is required for artifact conservation. Metal artifacts must be cleaned to remove corrosion, which can range from tarnishing to a thick crust, in addition to dust, previous coatings, and burial deposits. Cleaning corrosion is still a challenging conservation process, but the advantages of using traditional cleaning methods outweigh the disadvantages. The current study aimed to evaluate the use of a nanosecond infrared Q-switched Nd: YAG pulsed laser for biodeteriogen elimination by laser cleaning and elemental analysis via LIBS analysis on old, corroded coins. The corroded coins used in this study were found in Egyptian burial dirt. Four different varieties of unknown corroded coins were exposed to laser cleaning testing. Throughout the cleaning process, LIBS diagnostics was used to monitor the laser ablation process as it removed various types of corrosion products. The coins were analyzed with a scanning electron microscope equipped with an energy-dispersive X-ray analyzer before and after the laser cleaning to assess the efficacy of the suggested laser setup technique used in this experiment (SEM-EDX). The results show a reduction in the spectral lines of corroded metals (Cu, Ca, and Mg) in the investigated coins after cleaning when compared to the original analyses. However, the surface morphology of each coin changes somewhat due to the presence of CuOx, which was recognized by increasing the strength of O lines, ensuring the viability of utilizing LIBS to identify the unknown coins tested.