Laser cleaning of oxide iron layer: Efficiency enhancement due to electrochemical induced absorptivity change

Laser cleaning experiments exhibited a higher cleaning efficiency of the laser cleaning upon application of electrochemical potential on an oxidised iron surface. The objective of this study is to clarify the role of such an electrochemical control on cleaning efficiency. Therefore a study by optical spectrometry at normal incidence in the relevant conditions was performed. From these measurements the optical parameters n and k were deduced. While n is mainly not affected, k changes for a factor of 10 upon application of an electrochemical potential. These results explain the differences in laser cleaning efficiency due to the modified absorption length. PACS: 78.20.Ci; 81.65.Cf; 81.65.Mq Corrosion in industry is a problem for all installations. The classical techniques of surface cleaning are based on mechanical or chemical methods. Thus the substrate may be damaged or polluted. Laser cleaning might be an interesting alternative for this purpose. Two methods were studied up to now in this context, laser ablation of the oxide layer at strong fluence (E ≥ 1 J/cm2) [1, 2] and the generation of acoustic waves by laser irradiation at low fluence (E ≤ 0.6 J/cm2) [3, 4]. The later allows to work below the ablation threshold of the substrate. It was shown that the environment (e.g. gas, liquid, ...) plays an important role on the efficiency of the laser cleaning [5–7]. Furthermore experimental studies [8, 9] have shown that laser cleaning on the oxide layer is more efficient when additionally electrochemical potential of suitable sign and size is applied before or during the cleaning process. The aim of this study, is to understand the role of such an electrochemical control on the laser cleaning of an oxidised surface.