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Publication Number: FHWA-HRT-09-044
Date: October 2009

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The findings of both research studies comprise the following general conclusions of this report:
  • Exposure of U-bend specimens fabricated from 16-mm-diameter 2304 SS to simulate pore solution with chlorides at ambient temperature and 65°C failed to reveal any susceptibility to stress corrosion cracking.

  • The critical chloride concentration required to initiate the corrosion of 2304 SS specimens polarized to +100 mVSCE while exposed to simulated pore water to which chlorides were incrementally added ranged from 5.00-9.86 wt percent Cl-.

  • No definitive corrosion initiation occurred after 929 days for three concrete slab specimens with 2304 SS reinforcement that were ponded with a Cl- solution. For one specimen, some momentary activity followed by repassivation occurred.

  • The Cl- threshold to initiate active corrosion of 2304 SS in concrete was greater than 12.5 kg/m3(4.51 wt percent cement).

  • An accelerated corrosion test was developed for weathering steel corresponding to a range of exposure conditions that demonstrated sensitivity to chloride environments.

  • The protective oxide layer (patina) of weathering steel was degraded above 0.5 wt percent chloride. Above 1 wt percent chloride, the protective oxide was severely degraded.

  • Sensors indicated the corrosion rate of coupon material exposed to the same environment.

  • Sensors allowed direct and immediate observation of the impact of environmental changes on corrosion rate.

  • XRD showed that the corrosion products produced in cycle test chambers were similar to those observed under field conditions.

  • Bridge cable sensors were capable of monitoring corrosive conditions within suspension bridge cables and other occluded geometries.


United States Department of Transportation - Federal Highway Administration