Removal of embedded contamination in chlorinated rubber coatings using a portable high power diode laser

In this article we report the process characteristics for removing embedded contamination in white chlorinated rubber (CR) coatings from concrete surfaces utilizing a portable 120 W continuous wave diode laser operating at 810 nm wavelength and applying a cylindrical focusing system. Coating layers of 350 μm thickness have been prepared to industrial standards. A contaminant simulant ZrO2 layer was embedded in the coating. The coatings were subsequently removed by the laser with the aid of oxygen process gas. The reflectivity properties of the CR material from the visible to the near infrared wavelengths, as well as their behavior under high temperatures have been examined with a normal incidence reflectance spectrometer. Even though the reflection coefficient of white CR at 810 nm is almost 100%, a drop in reflectivity after a brief period of laser irradiation explains the initiation and the sustaining of the combustion process and the subsequent coating removal. The sizes of the generated airborne particles are measured and interpreted. The removal quality and efficiency dependence on laser parameters are assessed and discussed, together with safety aspects regarding portable laser paint removal process. An attempt is made to interpret the mechanisms involved in the removal process. The remaining surfaces were then analyzed via optical microscopy, by energy dispersive analysis of x rays and total reflectance x-ray fluorescence, to establish the effectiveness of the embedded contaminant simulant removal.