Bridge coatings greatly contribute to the longevity of steel bridges 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), otherwise the bridge may have to be completely overcoated or the coating be removed and replaced prematurely. This approach has proven to be a maintenance challenge for bridge owners. While efforts are ongoing to improve the service life of traditional coating systems another approach would be the use of “duplex systems” (hot dip galvanized or metallized with a coating system) to provide long-term protection against corrosion. Research indicates that the synergetic life of duplex coatings will extend the bridge service life beyond the traditional coating systems. Unfortunately, bridge owners have had mixed experience with duplex coatings. Some state departments of transportation (DOTs) have had great success with the duplex coating systems 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 coating systems sooner than anticipated. The processes are currently reliant on the experience of the galvanizers, metalizers, and coating applicators with lack of guidelines. As a result and in order to be consistent, there is an immediate need to develop guidelines for bridge owners on the use of duplex coating systems for corrosion protection of steel bridges.
The objectives of this research are to (1) develop AASHTO guidelines for corrosion protection of using duplex coating systems for extending the service life of steel bridges that can be adopted by AASHTO and (2) plan and conduct a workshop to demonstrate the use of proposed guidelines to an audience of DOT staff and other stakeholders. The guidelines shall cover the selection and application of duplex coating systems during the new design, and maintenance and rehabilitation of existing steel bridges.
Task 1. Conduct a literature review of relevant domestic and international research considered to be the state-of-the-practice for corrosion protection of steel bridges. The domestic review shall include research conducted through the NCHRP; FHWA; and other national, industry, state, and pooled-fund sponsored research.
Task 2. Synthesize the literature review to identify the knowledge gaps for steel corrosion protection systems. Discuss the quantity and quality of data required to achieve the project objectives. These gaps should be addressed in the final product or in the recommended future research as budget permits.
Task 3. Propose laboratory testing and case studies to be executed in Phase II. The Task 3 work plan shall be presented in a matrix format that includes laboratory test types and issues related to the application of corrosion protection systems (e.g., adhesion, finish coats, surface preparation, current field applied paint systems, and galvanizing and metallizing). For each case study, identify the required data to be collected in order to achieve the research objectives and collect data from at least eight agencies for data collection considering diverse bridge attributes (e.g., location, structure type, steel type, environment, and coating age). NCHRP must give prior approval of agency selection.
Task 4. Prepare Interim Report No. 1 that documents Tasks 1 through 3, includes the data archiving plan (see Special Note C), and provides an updated and refine work plan for the remainder of the research no later than 4 months after contract award. The updated plan must describe the process and rationale for the work proposed for Phases II though IV.
PHASE II— Laboratory Testing and Case Studies
Task 5. Execute Task 3 according to the approved Interim Report No.1
Task 6. Propose a method, for execution in Phase III, to establish the criteria and processes for selection of bridge duplex coating protection systems for (1) design of new steel bridges, (2) and maintenance and rehabilitation of existing steel bridges for enhancing the performance of the coating systems and extend service life. In addition, provide criteria for field and shop applications of corrosion protection systems.
Task 7. Prepare an annotated description of each section and subsection of the proposed guidelines along with the expected level of detail of each subsection.
Task 8. Prepare Interim Report No. 2 that documents the results of Tasks 5 through 7 and provides an updated work plan for the remainder of the project. This report is due no later than 12 months after approval of Phase I. The updated plan must describe the work proposed for Phases III through IV.
PHASE III—Proposed AASHTO Guidelines
Task 9. Execute Tasks 6 and 7 according to the approved Interim Report No.2. Submit a report documenting both tasks for NCHRP approval no later than 7 months after approval of Phase II.
Task 10. After NCHRP approval of the draft guidelines, plan and conduct a workshop with 20 representatives of bridge owners and other stakeholders to review the draft proposed guidelines and implementation plan. Revise the draft proposed guidelines and workshop materials taking into account feedback gathered during the workshop.
Task 11. Prepare Interim Report No. 3 that documents and summarize the results of Tasks 9 and 10 no later than 9 months after approval of Phase II.
PHASE IV—Final Products
Task 12. Revise the proposed AASHTO guidelines and workshop materials taking into account comments from the NCHRP project panel and prepare a ballot item for the AASHTO Highway Subcommittee on Bridges and Structures consideration.
Task 13. Prepare final deliverables including: (a) a final report that documents the entire research effort and (b) the proposed AASHTO guidelines and ballot, workshop materials, and implementation plan.
STATUS: Research in progress