The following new findings and concepts are expected to lead to a better understanding of the role of surface preparation profile in coatings performance. Scanning electron microscopy and related techniques (especially in 3-D stereo) made it possible to visualize, for the first time, the true topography of structural steel surfaces cleaned by various methods and to reconstruct the probable mechanism of profile formation. Exposure tests still under way have already established important trends: abrasive size and profile height, within normal ranges, had a relatively minor effect on coatings performance; increasing the degree of surface preparation yielded diminishing returns; sand and other non-metallic blast media gave consistently good results. Primer thickness was very critical. These and other major variables (angle of impingement, oiliness, rolling direction, pre-rusting, steel thickness, etc.) are still the subject of continuing exposures. A proposed specification has been developed for a standard method of measuring profile by optical microscopy. An (h sub max) concept was developed ot inter-relate four good field methods which formerly had yielded wide discrepancies in measuring profile (visual comparator, depth age, magnetic gage, and replica tape/gage). Three additional methods were found to be especially effective in research studies: (microsections, stylus traces, and a triangulation technique), whereas four other approaches are of special future interest (surface volume, pneumatic, scratch gage, and light-section gage). The effects of the major surface preparation parameters on profile were established including type of abrasive, size of abrasive, degree of blast cleaning, type of equipment, angle of impingement, steel thickness, peak count, and steel variation.

  • Supplemental Notes:
    • Sponsored by Pennsylvania DOT and conducted in cooperation with DOT, Federal Highway Administration.
  • Corporate Authors:

    Carnegie Mellon Research Institute

    Rail Systems Center, 700 Technology Drive, P.O. Box 2950
    Pittsburgh, PA  United States  15230-2950
  • Authors:
    • Keane, J D
    • Bruno, J A
    • Weaver, REF
  • Publication Date: 1976-6-30

Media Info

  • Pagination: 169 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00158071
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: FHWA-PA-71-14 Final Rpt.
  • Contract Numbers: FPC-40M3213
  • Files: TRIS, USDOT
  • Created Date: Oct 13 1977 12:00AM