Treatments in pulsed laser for the selective removal of corrosion products on metallic artefacts [Trattamenti in laser pulsato per la rimozione selettiva di prodotti di corrosione su manufatti metallici]

Laser cleaning treatments have been used in the field of cultural heritage from several years. The conservation of the archaeological metallic artefacts requires the development of non-invasive cleaning techniques, more and more accurate and selective, able to remove the corrosion products without altering the artefacts surface. A series of copper samples were coated with layers of corrosion products artificially grown electrochemically or by immersion in solutions containing sulphates and chlorides. The samples were then cleaned with a fiber laser (λ = 1064 nm), operating in a pulsed modality (Q-switched Yb: YAG laser), coupled to a CAD-like system (EzCAD 2.1 UNI), and allowing scanning the surface under controlled conditions. From the experimental findings it is possible to extrapolate, for constant irradiance, the most suitable parameters (pulse frequency, surface scanning conditions, etc.) in order to selectively remove the layer of oxy-chlorides.