The National Academies

NCHRP IDEA 20-30/IDEA 155 [Completed (IDEA)]

Corrosion-Resistant, Structurally Reinforced Thermal Spray Coatings for In-Situ Repair of Load Bearing Structures
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Inam Jawed
Fiscal Year: 2011

This project was aimed at developing and demonstrating the feasibility of in-situ reclamation of corroded components in load bearing infrastructures (such as bridges) providing robust corrosion protection with high-velocity thermal spray coating. Work in Stage 1 focused on the mechanical behavior of the optimized thermally-sprayed reclaimed steel. Initial efforts used Fe or Ni as the reclaimant material deposited using the high velocity oxy-fuel (HVOF) thermal spray process. Process optimization with in-situ monitoring of residual stresses demonstrated that compressive residual stresses could be achieved in HVOF reclamation material. Mechanical testing to date shows that in almost all cases, the addition of the coating shows load recovery and enhancement in yield stress. This suggests good coupling between the reclaimed material and the parent metal as well as demonstration of load bearing capability of the HVOF coating. Detailed comparisons between Fe and Ni coatings were made. At thin coatings, the Ni deposited ones presented a better performance compared to the Fe-based ones, since they were able to endure excessive loads and displacements without delamination. However, both coatings presented an increased load bearing capacity compared to virgins –uncoated- tensile test specimens. At thick coatings, new spraying parameters were required in order to produce more compressive coatings, as they were showing premature failure. The new compressive Ni coatings presented the highest load bearing capacities, compared to all coatings and virgin tensile specimens. The composite repaired structure with Nickel overlay also shows excellent corrosion resistance. Concurrently, efforts were initiated aimed at understanding of the operative mechanisms on strength reclamation via finite element modeling and experiments. Results to date appear promising and represent a good transition opportunity. The next step in furthering and implementing this technology is consider a larger scale component demonstration as well as future transfer of the IDEA results into practice. For this active involvement of state DOTs is needed and being solicited.

The contractor's final report is available.

To create a link to this page, use this URL: http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3238