This project demonstrated the innovative Thermal Spray Vitrification (TSV) process to remove lead-based paint from a steel bridge at the Rock Island Arsenal in Illinois, and from an aircraft hangar at the Marine Corps Base in Kaneohe Bay, Hawaii. In the patented TSV process, a specially formulated iron silicate glass powder is flame-sprayed on to a painted surface. Lead ions are absorbed into the molten glass as it spreads over the surface and are trapped within the silicate matrix. As the glass cools, the glass layer spontaneously spalls from the surface for collection and disposal. The TSV process avoids some of the U.S. Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) compliance requirements for containment, worker safety, and hazardous waste disposal associated with removing hazardous lead-based paint by conventional abrasive blasting. The latter can also produce up to 15 pounds of hazardous waste per square foot of treated surface.
Paint removal was successfully completed, while meeting all applicable environmental and occupational health standards, at an estimated rate of 30 square feet per hour for the bridge and 35 square feet per hour for the hangar door. One to three passes of the TSV process were required. Cooling the backside of thin steel sections with an air-water mist during the pre-heating stage minimized any possibility of warping of the underlying structures. The State of Illinois EPA did not require any special permit for the complete removal process, and remelting the vitrified glass for a minimum of 5 hours resulted in a non-leachable, non-hazardous waste.
TSV costs were estimated at $5 per square foot for the bridge and $3.50 per square foot for the hangar door, which are at the low end of the cost ranges for alternative technologies. Cost is impacted by the complexity of the structure and the thickness of the existing paint. The U.S. Department of Defense (DoD) owns more than 200,000,000 square feet of steel structures coated with lead-based paint. Assuming that 10 percent need paint removal and half can use the TSV process at a cost avoidance of $3 per square foot compared to currently used technologies, the potential DoD-wide benefits are $30 million over the next 10 years.
The TSV process appears most appropriate for zonal paint removal in preparation for repairs to large structures, or for paint removal from smaller fixed structures such as fire hydrants where containment would represent a large portion of the overall cost for conventional methods. TSV is also attractive in remote locations where hazardous waste disposal facilities are not available. Protective clothing, respirators, and testing are still recommended for workers conducting TSV removal even though emission of lead and other contaminants is minimal. TSV is not applicable to lead-based paint removal from wood, concrete, or masonry structures. (Project Completed - 1999)