Field Evaluation of Zinc-Based Protective Coatings for Structural Steel

摘要

A variety of factors and developments in recent years has significantly affectedbridge painting operations for transportation agencies. Extensive highway and bridge construction in the 1950's and 60's have produced a large number of structures that are now in the age range of 25 to 45 years. The structural steel on many of these existing bridges contain paint systems that are approaching, or have passed the end of their service lives, creating the need to identify appropriate remedial action for various circumstances. The banning of lead-based paint in the 1980's has also created a need to identify new coating systems that maximize durability when applied under field conditions. Other significant developments include the strengthening of health and environmental regulations directed at the removal of existing lead-based paint in the field. These developments have raised the importance of painting issues within a state bridge management programs. To address these trends, the Connecticut Department of Transportation initiated an FHWA-sponsored research project to evaluate high-performance coating systems for existing steel bridges. The following two systems were chosen for full-scale, field evaluation: a three-cost system, containing a pure metal, zinc/aluminum alloy primer, applied by thermal spraying; and, a three-coat, all paint system, containing an organic zinc-rich primer. These systems were applied to portions of four bridges between 1987 and 1991, and evaluated through July 1995. The report describes the installation of the coatings, and provides service life estimated based on field evaluation data obtained to date. This information, combined with cost data, was then used to identify appropriate applications for each system.