Investigation of the chemical composition, surface structure, metallurgical features,
corrosion mechanism and surface modification techniques of archaeological metallic
artifacts from Romans and pre-Romans times aimed to simulate the most commonly used
Cu and Ag-based alloys. These simulated reference alloys will be used as sacrificial
materials to study the most appropriate conservation materials and procedures. In the present
work, Laser Induced Breakdown Spectroscopy (LIBS) is introduced as a new validated
surface mapping technique to study the micro-chemical distribution of elements in binary
reference copper-silver alloy samples. Using different techniques for surface and bulk
2
analysis, such as Scanning Electron Microscopy coupled with Energy Dispersive X-ray
spectroscopy (SEM-EDS) and X-ray Diffraction (XRD), it has been proven that LIBS is a
simple, sensitive and direct technique in the determination of heterogeneity of the sample’s
surface. By changing the laser wavelength (λ/nm) and focal length of the used focusing lens
(f/cm), different spot sizes can be obtained. It was possible to control the spatial resolution
in mapping the investigated samples’ surface and to achieve local chemical information. In
the present work, Q-switched Nd:YAG laser has been used at its fundamental wavelength
1064 nm and its second harmonic 532 nm. The studied samples were specially manufactured
heterogeneous copper-silver alloys with known grain size as studied via SEM investigation.
The obtained LIBS results are in good agreement with the other used analytical techniques
and extend the applicability of the surface techniques to study metallic ancient objects.
