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 surf aces utilizing a portable 120 W continuous wave diode laser operating at 81 0 nm wavelength and applying a cylindrical focusing system. Coating layers of 350 mu m thickness have been prepared to industrial standards. A contami nant simulant ZrO2 layer was embedded in the coating. The coatings were sub sequently removed by the laser with the aid of oxygen process gas. The refl ectivity properties of the CR material from the visible to the near infrare d 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 refl ectivity after a brief period of laser irradiation explains the initiation and the sustaining of the combustion process and the subsequent coating rem oval. The sizes of the generated airborne particles are measured and interp reted. The removal quality and efficiency dependence on laser parameters ar e assessed and discussed, together with safety aspects regarding portable l aser 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 r eflectance x-ray fluorescence, to establish the effectiveness of the embedd ed contaminant simulant removal. (C) 2000 Laser Institute of America. [S104 2-346X(00)00603-3].