Recent regulations concerning volatile organic compounds (VOCs) and certain hazardous heavy metals have had an impact on the construction and maintenance practices of transportation authorities. Powder coatings are a 100% solids material that are heat cured, thus they have near-zero VOC emissions during application. This report presents the results of an evaluation of various powder coatings designed to protect atmospherically exposed steel and reinforcing steel from corrosion. Three categories of coatings were selected for the test program: a solvent-based control system, 13 proprietary single-coat powder systems, and 6 two-coat powder coating systems. The coatings were evaluated over three substrates: abrasive-blasted A36 steel, abrasive-blasted A588 steel, and cold-rolled A36 steel with a zinc phosphate pretreatment. Testing included a cyclic salt fog/natural marine exposure, a cyclic brine immersion/natural marine exposure, a natural marine exposure test, water penetration test, anodic disbondment test, and electrochemical impedance spectroscopy tests, and coated rebar exposure in concrete. Underfilm corrosion and subsequent coating disbondment was the significant failure mode of the powder coatings. Surface preparation, coating thickness, and coating holidays all contribute to powder coating performance. Using a zinc-containing primer or powder was the most effective means of controlling this phenomenon, though the data suggests that various zinc-containing materials are not necessarily equally effective at eliminating underfilm corrosion. Gloss- and color-retention characteristics were typical of the generic powder coating resin materials. Polyesters and acrylics had superior gloss retention, while epoxies and polyvinyl chloride (PVC) powders had significant chalking over the exposure periods.

  • Corporate Authors:

    Ocean City Research Corporation

    Tennessee Avenue and Beach Thorofare
    Ocean City, NJ  United States  08226

    Federal Highway Administration

    Turner-Fairbank Highway Research Center, 6300 Georgetown Pike
    McLean, VA  United States  22101
  • Authors:
    • Ault, J P
    • Farschon, C L
  • Publication Date: 1995-6


  • English

Media Info

  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 69 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00720246
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-RD-94-175, 3E4a0272
  • Contract Numbers: DTFH61-91-C-00019
  • Files: TRIS, USDOT
  • Created Date: Apr 22 1996 12:00AM