Application of low temperature plasmas for restoration/conservation of archaeological objects

Abstract

The low temperature low-pressure hydrogen based plasmas were used to study the influence of processes and discharge conditions on corrosion removal. The capacitive coupled RF discharge in the continuous or pulsed regime was used at operating pressure of 100-200 Pa. Plasma treatment was monitored by optical emission spectroscopy. To be able to study influence of various process parameters, the model corroded samples with and without sandy incrustation were prepared. The SEM-EDX analyzes were carried out to verify corrosion removal efficiency. Experimental conditions were optimized for the selected most frequent materials of original metallic archaeological objects (iron, bronze, copper, and brass). A special focus was kept for the samples temperature because it was necessary to avoid any metallographic changes in the material structure. The low pressure hydrogen plasma is not applicable for objects with a very broken structure or for non-metallic objects due to the non-uniform heat stress. Due to this fact, the new developed plasmas generated in liquids were applied on selected glass materials. The original archaeological objects were used in this case because it was very complicated to prepare a uniform artificial corrosion layer at laboratory conditions.The low temperature low-pressure hydrogen based plasmas were used to study the influence of processes and discharge conditions on corrosion removal. The capacitive coupled RF discharge in the continuous or pulsed regime was used at operating pressure of 100-200 Pa. Plasma treatment was monitored by optical emission spectroscopy. To be able to study influence of various process parameters, the model corroded samples with and without sandy incrustation were prepared. The SEM-EDX analyzes were carried out to verify corrosion removal efficiency. Experimental conditions were optimized for the selected most frequent materials of original metallic archaeological objects (iron, bronze, copper, and brass). A special focus was kept for the samples temperature because it was necessary to avoid any metallographic changes in the material structure. The low pressure hydrogen plasma is not applicable for objects with a very broken structure or for non-metallic objects due to the non-uniform heat stress. Due to this fact, the new developed plasmas generated in liquids were applied on selected glass materials. The original archaeological objects were used in this case because it was very complicated to prepare a uniform artificial corrosion layer at laboratory conditions.