Laser removal of chlorine from historical metallic objects

Abstract

This study is focused on the selective laser removal of chlorine-containing corrosion products from artificially corroded samples of copper, brass and steel. Its goal is to find an efficient methodology for laser cleaning of historical metallic objects. The laser treatment is done with two laser sources: Q switched Nd:YAG laser generating nanosecond pulses at 1 Hz repetition rate in the IR (1064 nm) and the green (510.6 nm) spectral range, and copper bromide vapor laser (CuBrVL) generating nanosecond pulses at 20 kHz repetition rate in the green (510.6 nm) spectral range. The cleaning is performed in dry and wet conditions. The surfaces before and after the treatment are characterized using optical microscopy (OM), x-ray fluorescence spectroscopy (XRF), x-ray diffraction spectroscopy (XRD), and laser-induced breakdown spectroscopy (LIBS).