United States Department of Transportation
i
Issues Impacting Bridge Painting: An Overview
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1995-08-01
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[PDF-4.44 MB]
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Abstract:This final report documents the findings of a research program designed to collect and critically assess information on issues impacting bridge painting. Life-cycle costs and performance were used to assess the economics of maintenance painting. These assessments are made difficult (uncertain) because performance data and hidden application costs are extremely variable. The variability of coating performance can be improved by better control of preparation quality. Paint-removal assessments were made based largely on field operations. A few tests involving environmental chambers were conducted. Test conditions and pros and cons of the various procedures are critically summarized. Regarding worker safety, recommendations are made for close monitoring and control of the particles generated during surface preparation, especially when techniques such as steel-grit blasting and laser ablation are used for cleaning. Paint debris digestion procedures followed by atomic absorption spectroscopy is the best way to determine total lead in a paint film. The toxicity characteristic leaching procedure (TCLP) is currently the best method for classifying paint, but may not be a reliable indicator of future resistance to leaching. Steel blast media is recyclable and stabilizes lead; proprietary additives work well in reducing leachable lead in the TCLP. Long-term stability of lead-containing debris has not been validated. With the exception of thermal spray coatings, the lack of performance data, i.e., long-term durability data, is a major problem in using advanced coating systems. Advantages and disadvantages of thermal spray coatings are summarized. Modified accelerated testing procedures to determine coating durability were identified that could improve the correlation between laboratory tests and corresponding field tests. Several sensor technologies were considered in an effort to identify techniques that could improve the quality of applied coatings. The methods evaluated included monochrome CCD (to determine the degree of surface rusting), color CCD to assess the cleanliness of blast-cleaned surfaces, and thermal-wave images to evaluate the condition of the substrate beneath the coating prior to paint removal.
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