Repair and Restoration of the Optical Properties of Sandblasted Glasses By Silica-Based Sol-Gel Coatings

The damage provoked by sand storms in Sahara desert to windscreen of vehicles and solar mirrors is a problem. Different solutions have been proposed, one of them is the application of polymeric coatings, but they rapidly degrade. In this work, we have deposited silica-based sol-gel coatings including silica nanoparticles onto sandblasted glasses. The glasses were eroded by sandblasting varying the projected sand mass and the incidence angle to obtain different surface states. The eroded samples were coated by dipping with a silica layer to correct the defects induced by sandblasting and restore the optical transmission. The damage increases with increasing projected mass and the impact angle. The optical transmission decreases with increasing damage. In extreme conditions, optical transmission falls from 91.5% to 68.6%. The deposition of silica-based layers containing SiO2 colloidal nanoparticles promotes the repairing of sandblasting defects. A strong decrease of roughness to values similar to those of as-received glass is related with the increasing of the optical transmission up to levels permitting of windscreens and solar mirrors. Transmittance measurements showed a remarkable improvement in all cases, whatever the projected sand mass or the impact angle. For highly degraded samples, the transmission increases from 68.6% to 91.4%, an improvement of near 23%.