Effective Use of Duplex Coating Systems to improve Steel Bridge Structure Durability

Steel bridge coatings greatly contribute to the longevity of a bridge structure and reduce the total life-cycle cost by protecting steel bridge members from corrosion. For most steel bridges across the nation, the most popular practice is to provide a 3-coat, zinc-rich primer system. The 3-coat system generally requires regular maintenance (touchup) and may have to be completely overcoated or repainted after as little as 15 years. This approach has proved to be a maintenance challenge for bridge owners. While efforts are ongoing to improve the service life of traditional paint systems, another approach would be the use of duplex systems (hot dip galvanized or metallized with a traditional finish coat) to provide long-term protection against corrosion. The combination of a metallic coating and a traditional finish coat is often referred to as a “duplex coating.” Van Eijnsbergen suggests that the synergetic life of duplex coatings is 1.5 to 2.3 times the sum of the individual lives, which may result in service lives in excess of 75 years. Unfortunately, bridge owners have had mixed experience with duplex coatings (including the galvanizing and metalizing process and/or finish coat application). Some state departments of transportation (DOTs) have had great success with the approach while others have had issues with galvanizing and metalizing quality, experienced adhesion problems with the finish coating, or have had to perform maintenance painting of the duplex system sooner than anticipated. The processes are currently reliant on the experience of the galvanizers, metalizers, and coating applicators and as such may be considered more of an art than a science. The proposed project will close the gap between art and science by developing design guidelines, guide specifications, and a state of the art report. The objective of this research is to develop practical guidelines that allow bridge engineers to position duplex coating systems among alternative corrosion control options for steel bridge structures. The researcher shall use a combination of laboratory testing and field studies to accomplish the project objectives.


  • English


  • Status: Proposed
  • Funding: $500000
  • Contract Numbers:

    Project 12-117

  • Sponsor Organizations:

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Dekelbab, Waseem

  • Start Date: 20180619
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01672545
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 12-117
  • Files: TRB, RiP
  • Created Date: Jun 18 2018 3:03PM