This report describes a 4-year bridge and test fence evaluation of protective coatings for maintaining weathering steel bridges. The test specimens consisted of steel panels cut from existing aged weathering steel bridges, along with some new mill scale bearing weathering steel as a control. The condition of the specimens ranged from extensively pitted and corroded (from chloride exposure) to mildly corroded and non-pitted. Specimens were cut from angle irons, stiffeners, cover plates, and web areas of bridges. Three methods of surface preparation were used: dry abrasive blasting, wet abrasive blasting, and power tool cleaning using rotary peening and non-woven abrasive discs. The chloride levels of the test specimens were measured after surface preparation to determine the coatings' ability to tolerate different levels of chloride or other soluble salts on the surface. Chloride levels measured ranged from less than 5 to 150 microg/sq cm. The test specimens were exposed at five sites, which included three bridges (Michigan, Pennsylvania, and Louisiana) and two test fence locations: a severe marine site and a moderate industrial site. The following six coating systems were applied to each combination of surface preparations, steel conditions, and sites: epoxy zinc rich system, urethane zinc-rich system, epoxy mastic system, ethyl silicate zinc/vinyl system, water-borne alkali silicate/acrylic system, and oil-alkyd control. Additional systems tested included a thermal spray zinc system and a low VOC ethyl silicate system. The rusting and scribe undercutting of the test panels were evaluated over a 4-year period. The data were analyzed using comparison of means, analysis of variance, and linear correlation methods. The effect of each variable was evaluated and a comparison made between the ranking of the coatings in the field testing compared to the various types of laboratory testing. A total of 564 specimens was included in the test matrix. Each combination of surface preparation, coating system, substrate type, and test site was replicated. Based on these data and evaluation of other bridge studies, a set of guidelines was developed for maintenance coating of weathering steel bridges. Recommendations were given for three field conditions: new A-588, non-corroded weathered A-588 (low-chloride), and corroded (weathered) A-588 (high chloride). Recommendations were also based on the bridge exposure conditions which were classified as severe or mild/moderate.

  • Supplemental Notes:
    • See also FHWA-RD-91-087, "Maintenance Coating of Weathering Steel: Interim Report", December 1991 (SSPC Report 91-04) (TRIS 622324).
  • Corporate Authors:

    Steel Structures Painting Council

    4400 Fifth Avenue
    Pittsburgh, PA  United States  15213

    Federal Highway Administration

    Turner-Fairbank Highway Research Center, 6300 Georgetown Pike
    McLean, VA  United States  22101
  • Authors:
    • Appleman, B R
    • Weaver, REF
    • Bruno, J A
  • Publication Date: 1995-3


  • English

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 130 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00675293
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: FHWA-RD-92-055, SSPC Report 92-03, 3E4c0112
  • Contract Numbers: DTFH61-84-C-00063
  • Files: TRIS, USDOT
  • Created Date: Mar 16 1995 12:00AM