Details:

Creators:
McGill, Galen E. ; Cramer, Stephen D. ; Corvino, Bernard S. ; Bullard, Sophie J. ; Holcomb, Gordon R. ; ... More +
McGill, Galen E. ; Cramer, Stephen D. ; Corvino, Bernard S. ; Bullard, Sophie J. ; Holcomb, Gordon R. ; Collins, W. Keith ; Govier, R. Dale ; Wilson, Rick D. Less -
Corporate Creators:
Oregon. Dept. of Transportation. Research Unit
Corporate Contributors:
United States. Federal Highway Administration
Subject/TRT Terms:
[+]
Bridge Maintenance Bridges Cathodic Protection Concrete Reinforced Concrete Thermal Spray Titanium Anode
Publication/ Report Number:
FHWA-OR-RD-99-13
Resource Type:
Tech Report
Geographical Coverage:
United States ; Oregon
United States ; Oregon Less -
TRIS Online Accession Number:
00762988
OCLC Number:
40768217
Edition:
Final Report
Corporate Publisher:
Oregon. Dept. of Transportation
Abstract:
This study provided the first field trial of a catalyzed, thermal-sprayed titanium anode for cathodic protection of steel reinforced concrete structures. Catalyzed titanium as an anode material offers the advantage of long life due to the inherent non-corrosive nature of the metal in atmospheric exposure. To continue to serve as an anode, the titanium will require a periodic and easily accomplished re-application of the catalyst rather than re-application of the metal. The purpose of this study was to evaluate the installation and operation of the catalyzed titanium anode and to evaluate the economics of the titanium anode system compared to thermal-sprayed zinc. The initial phase of the study included modification of the spray equipment for spraying titanium wire and determination of the optimal spray parameters for applying the titanium anode to the bridge. Coating resistivity was found to be the best measure for evaluating the effectiveness of the coating. Decreasing spray distance, increasing current, and using nitrogen as the atomizing gas (propellant) all decrease coating resistivity. A multiple regression equation developed from the collected data showed that, for the data collected in this study, spray gun travel speed and atomizing gas pressure have an insignificant effect on coating resistivity Coating analysis showed that the arc-sprayed titanium is a non-homogeneous coating due to reactions with atmospheric gases. The coating contains, on average, 88 weight percent titanium. The principal coating constituents are α-Ti containing interstitial nitrogen and interstitial oxygen, and γ-TiO with the possibility of some TiN. The coating consists of alternating layers of α-Ti rich and γ-TiO rich material. The use of nitrogen as the atomizing gas results in a coating with less cracking, more uniform chemistry, and therefore, lower coating resistivity than is produced using air atomization. The field trial resulted in installation of 280 m2 (3015 ft2 ) of catalyzed, arc-sprayed titanium on the Depoe Bay Bridge. Several lessons were learned during the field trial. Although use of a grade 1, annealed titanium wire for spraying was found to reduce equipment wear, frequent equipment maintenance caused by rapid wear of the copper spray tips had a significant impact on operator productivity. The switch mode power supply furnished with the spray equipment was unable to provide the stable arc needed for smooth operation of the spray equipment. Current distribution plates embedded flush in a concrete patch material proved to be the best method for providing a low resistance connection between the anode and the power supply. Although some difficulty was experienced during the field trial, the costs for performing this work exceeded the bid costs for installing arc-sprayed zinc on this same structure by just 18 percent. If the long-term performance of the catalyzed titanium anode system is proven, the arc-sprayed titanium system will provide a life cycle cost advantage over the arc-sprayed zinc system.
Format:
PDF
Funding:
SPR 365
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:0fe65fe223690c7d4f5ba905b99bf03422285e65453bea570caffe6f392bf541
Download URL:
https://rosap.ntl.bts.gov/view/dot/14434/dot_14434_DS1.pdf
File Type:

Supporting Files

• No Additional Files

More +