EXPERIMENTAL CULVERT PIPE, STH 80, JUNEAU AND WOOD COUNTIES, WISCONSIN

Culvert pipes of aluminum, aluminized steel, polymeric coated galvanized steel and epoxy bonded steel were placed at three sites in central Wisconsin in 1981 and monitored for their corrosion resistance. Galvanized steel apron end walls were attached to the pipes as a means of comparison of corrosion rates with zinc galvanized steel. The three sites selected were in areas where strong corrosiveness to zinc galvanized steel pipe was highly likely. Field tests of soil and water at the sites were made annually including pH, electrical resistivity and oxidation-reduction potential of the soil and water, dissolved oxygen content of the water and sulfide content of the soil. The pipes experienced corrosion originating from a variety of conditions including low pH of the soil and water, anaerobic sulfate reducing bacteria in the soil and water, and road salt. In comparing the performance of the four culvert types, the polymeric coated galvanized steel pipes appeared to best resist corrosion. None of the pipes were perforated and removal of the coating was localized to the vicinity of exposed rivet heads and section ends. The epoxy bonded steel pipes did not perforate but lost considerable coating at the two sites of flowing water and experienced advanced corrosion at joints at the site of equalizer pipes. This type of coating is no longer used. The aluminized steel pipe experienced localized perforation and localized pitting of the steel cores and inverts at localities of organic material. The protective cover of aluminum is ascribed to the development of an aluminum oxide coating on the metal and this coating appears to be degraded in more strongly reducing environments. The aluminum pipe evidenced the most severe distress and resulted in several instances of failure due to corrosion in forms of thinning of the metal roofs, perforations in the roofs, and coatings of white precipitate on the inner roofs of the pipes. This type of corrosion appears to be attributable to the presence of NaCl in chemical deicers (road salt). The aluminum pipes have, however, proved to be immune to corrosion in the natural environment. There has not been a reported case of perforation of an invert of an aluminum pipe from the water side in Wisconsin, but there were several aluminum pipes perforated from the soil side in areas of wet organic sandy soil. These pipes had replaced the zinc galvanized steel pipe that had been corroded by the actions of anaerobic sulfate reducing bacteria in the water. At this time, some aluminum culvert pipes with protective covering laid over the top are being installed in Wisconsin. The galvanized steel apron end walls unexpectedly experienced advanced corrosion at all three sites, and some perforation at one site. It appears that the type of pipe least susceptible to corrosion caused by moist organic soil, at sites where tests for anaerobic sulfate reducing bacteria in the soil are frequently positive, is a pipe with an organic barrier coating, such as polymeric coated steel.

Language

  • English

Media Info

  • Features: Appendices; Photos; Tables;
  • Pagination: 40 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00987682
  • Record Type: Publication
  • Report/Paper Numbers: WI/FEP-09-96,, Final Report
  • Files: TRIS, STATEDOT
  • Created Date: Mar 11 2005 12:00AM