INFRASTRUCTURE RESEARCH PROGRAM

Thermal Spray Technologies for Infrastructure Repair and Maintenance
C.Berndt, M.L.Allan**, H.Herman, J.Brogan, R.Benary, R.Zatorski and M.Leote*
Materials Science and Engineering
Brookhaven National Laboratory; Upton, NY 11973
* Triborough Bridge and Tunnel Authority; Randall's Island, New York, NY 10035

Introduction
Thermal spray involves the injection of feedstock materials into a high temperature heat source. The material is melted and propelled towards the substrate where it rapidly cools and forms a coating. Thermal spray has been used extensively by many industries over several decades to form protective and functional coatings. Thermal spray has re-emerged over the last 5 year as a viable and economic method of forming barrier and corrosion resistant coatings on infrastructure. Thermal spray technologies have the ability of on-site repair of infrastructure. Several major demonstrations of these activities have recently been carried out by the Thermal Spray Laboratory (TSL), SUNY-Stony Brook, under the support and auspices of the US Army Corps of Engineers, CERL, and the Triborough Bridge and Tunnel Authority, New York City. These programs are described below.

Removal of Lead-Base Paint
Traditional grit blasting of hydraulic structures and highway bridges potentially involves the wide distribution of lead contaminate some distance from work sites and inflicting unacceptable health risks. An alternative means of surface preparation, patented by the US Army Corps of Engineers, is on-site vitrification of hazardous waste. That is, thermal spraying of specially-developed molten glass to encapsulate and chemically stabilize lead-based paint and rust. The encapsulate is then removed by chipping-off relatively large chunks, which are readily removed for disposal. The objective has been to develop technology and guidance for maintenance where work will involve the removal of a coating material containing lead-based paint or other hazardous waste. Spray techniques and glass deposit chemistries and encapsulation effectiveness are being testing and optimized.

Automated Thermal Spray Technology
TSL has developed and demonstrated on Interstate 495 an integrated robotic advanced thermal spray coating system for field application to civil works infrastructure. Material feedstock products include, but are not limited to, thermally sprayed metallic corrosion/erosion resistant coatings such as zinc and aluminum-zinc alloys on steel structures, and thermally sprayed polymers (see below). The demonstration indicated that there was no need to completely contain the grit blasting procedure within the usual shroud since the vacuo-blast system was quite successful. Furthermore, the video camera observation and quality control system removed the coating applicator from a potentially hazardous and unsafe procedure; i.e., on the superstructure of a bridge. Such automation has the potential of increasing the overall process economics and efficiency of coating application.

Metal Sprayed Coatings
Successful experience of such coatings in the UK and Europe extends back to the 1940's. In the US, metal sprayed coatings are presently being specified and used by Florida DOT, ConnDOT, Caltrans, Oregon DOT, Ohio DOT and others. The conservative life time for a 10 mil thickness of Zn (or Zn-Al alloy) is ~25 years and can be extended a further 15 years by the application of an vinyl paint system. Initial application costs are $10.00 per square foot or ~$0.45 per square foot per year. Coatings can be applied as either sacrificial systems on metal structures or for impressed current cathodic protection of concrete structures. In the latter case, the sprayed coating acts as an anode which is connected to the rebar frame of the structure. Thus, corrosion and concrete disbondment of the structure can be completely mitigated.

Thermal Spray of Polymers
Working with industrial partners and local DOTs, TSL has demonstrated the utility of innovative hi-molecular weight and commingled/post consumer recycled polymer blends as low-VOC (volatile organic compounds) compliant coatings for thermal spray applications, with special attention to corrosion control of infrastructure systems. Material specifications for various polymer coating blends for thermal spray applications are being developed. A number of polymers have recently been combustion sprayed on various sections of the Triborough Bridge. These barrier coatings can be applied throughout the year - thereby extending the maintenance campaigns of infrastructure.

Outreach Activities
TSL, being an educational and research institution, has trained some 6 students specifically in the area of infrastructural maintenance and repair. The training includes both the fundamental theory and practical application of coatings on bridges of the TBTA and Region 10 of the NYS-DOT. TSL has representation within several professional societies on the following committees: National Association of Corrosion Engineers T6-H-45, American Welding Society C2, ASM International -Thermal Spray Society, and the Steel Structures Painting Council C.1.2.B. TSL has inaugurated a homepage on the WWW for infrastructure activities. The address is: /infra/

References

• Polymer spraying
  • J.A.Brogan, K.A.Gross, Z.Chen, H.Herman and C.C.Berndt, "Investigation of combustion sprayed hydroxyapatite/polymer composite coatings", pp. 159-164 of "1994 Thermal Spray Industrial Applications", Ed. C.C.Berndt and S.Sampath, Pub. ASM International, Cleveland, OH-US, 1994.
  • J.A.Brogan, J.Margolies, S.Sampath, H.Herman, C.C.Berndt and S.Drozdz, "Adhesion of Combustion-Sprayed Polymer Coatings", pp. 521-526 of 1995 Advances in Thermal Spray Science and Technology", Ed. C.C.Berndt and S.Sampath, ASM International, Materials Park, OH-USA, 1995.
  • J.A.Brogan, R.Lampo and C.C.Berndt, "Thermal Spraying of Polymers", Proc. 4th World Congress on Coating Systems for Bridges and Steel Structures, 1-3 February, 1995, St. Louis, MO-USA. pp. 200-212.
• Automated thermal spray system
  • R.Benary, R.V.Gansert, C.C.Berndt, S.Sampath, H.Herman and V.Hock, "Field Evaluation and Economic Impact of an Automated Thermal Spray System (ATSS) for Infrastructure Rehabilitation", pp. 621-626 of 1995 Advances in Thermal Spray Science and Technology", Ed. C.C.Berndt and S.Sampath, ASM International, Materials Park, OH-USA, 1995.
  • R.V.Gansert, R.Benary, C.C.Berndt, and H.Herman, "Automated thermal spray system (ATSS) for rehabilitation and maintenance of infrastructure", pp. 445-450 of "1994 Thermal Spray Industrial Applications", Ed. C.C.Berndt and S.Sampath, Pub. ASM International, Cleveland, OH-US, 1994.
• Metal spraying
  • C.C.Berndt, S.Reddy and M.L.Allan, "Optimization of Thermal Spray Parameters for Cathodic Protection of Reinforcement in Concrete", pp. 51-64 of Innovative Ideas for Controlling the Decaying Infrastructure, Ed. V.Chaker, Pub. NACE International, 1995.
  • C.C.Berndt, S.Reddy and M.L.Allan, "Thermal Spraying of Zinc onto Concrete", Proc. 4th World Congress on Coating Systems for Bridges and Steel Structures, 1-3 February, 1995, St. Louis, MO-USA. pp. 182.
• Removal of lead-base paint
  • J.Karthikeyan, J.Chen, G.A.Bancke, H.Herman, C.C.Berndt and V.T.Breslin, "Thermal Spray Vitrification Process for the Removal of Lead Oxide Contained in Organic Paint", pp. 599-604 of 1995 Advances in Thermal Spray Science and Technology", Ed. C.C.Berndt and S.Sampath, ASM International, Materials Park, OH-USA, 1995.

Acknowledgments
The authors are grateful to Tafa, Inc. (NH), Plastic Flamecoat (TX), the NY Science and Technology Foundation, Region 10 of the NYS-DOT, the TBTA and US-Army CERL for support in these activities.

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06/05/2003 JQ