TRB 92nd Annual Meeting January 13-17, 2013 Washington, DC

Session 748 – Steel Bridge Coating Systems, Part 2: Existing Structures – AHD30 January 16, 2013

Presented By: Eric Yermack, P.E. Vice President, Structures Co-Author Matthew Neary

Duplex Coating System

Bridge Survey Population

Industry Recommendations

Coating Specifications

Bridge Field Inspections

Paint System Performance

Performance Observations

Cost Comparisons

Recommendations

Yes

Topic

What & Why?

Discuss

Recommend

Finish

No Q&A

A hybrid method of corrosion protection, formed by painting over hot-dipped galvanized steel

ZINC PATINA • Zinc Oxide • Zinc Hydroxide • Zinc Carbonate

Extended corrosion resistance

Synergistic effect

– 1.5 to 2.3 times longer life

Economic benefit

– Lower life-cycle cost

Extend life of previously

hot-dipped galvanized structures

Ease of repainting

Owner preferences and requirements

Aesthetics

LEGEND:

- Truss

- Stringer

- Replaced

BRIDGES • 6 Truss Bridges – 7-Year Average Age • 3 Stringer Bridges – 3-Year Average Age • 1 Arch Bridge – 8-Year Average Age • 1 Replaced / Moved

11 Bridges Considered – 5-Year Average Age 10 of 11 Bridges over water

MATERIALS • Grade 50 (ASTM A707) Steel • Galvanizing – AASHTO M111 • Duplex Coating System (fascia girders only)

© 2012 American Galvanizers Association

Galvanizing: AASHTO M 111M (ASTM A123)

Repair of Galvanizing: ASTM A780

Surface Preparation: ASTM D 6386-99

Paint Application Timing: After one to two years of

atmospheric exposure

Paint: AGA (American Galvanizers

Association) provides guidance, but

does not specify exact Base Primers

and Finish Coats

https://www.galvanizeit.org/

Special Provisions supplement NJDOT Standard Specs

Follow AGA Duplex Systems Recommendations

Typical coating specifications:

Galvanizing : AASHTO M 111M (ASTM A123)

Base Primer: Intercure 420 (Epoxy, 4-7 mils)

Finish Coat: Interthane 990 (Polyurethane, 2-3 mils)

(Both supplied by International Protective Coatings)

Coating Application: Within

24-Hrs of hot-dip galvanizing

Steel Stringer (2011) Exterior faces of fascia beams coated only Minor chipping Coating Rating: 9

Steel Stringer (2008) Exterior faces of fascia beams coated only Flood debris accumulation Coating Rating: 8

Truss – Thru (2008) All truss members and stringers coated Poor adhesion Coating Rating: 8

Steel Stringer (2008) Exterior faces of fascia beams coated only Poor adhesion Coating Rating: 8

Truss – Thru (2007) All members coated Poor coating adhesion Coating Rating: 5

Truss – Thru (2006) All members coated Poor coating adhesion Coating Rating: 8

Truss – Thru (2005) All members coated Poor coating adhesion; touched-up areas Coating Rating: 8

Truss – Thru (2000) Truss coated only Red rust found Touched-up areas Coating Rating: 8

Truss – Thru (2004) All members coated Minor paint adhesion issues Coating Rating: 8

Arch (2004) All members coated Bubbling; poor adhesion; touched-up areas Coating Rating: 7

CO

ND

ITIO

N

YEAR CONSTRUCTED

Successful in inhibiting iron oxide corrosion

No visible damage to underlying zinc coating

Localized chipping – possibly due to handling or debris collision

Paint adhesion issues present on all structures

Paint flaking in some large, localized areas

Paint failure in areas of debris buildup

Cracking of paint over welds

Gusset plates were a common failure location

Truss members performed well by comparison

Maintenance touch-up painting was effective

Inadequate surface preparation

Use of paint incompatible with zinc

Moisture or debris present on paint surface

Insufficient or excessive galvanizing thickness

Influence of irregularly shaped components (gusset plates) and weld metal

Timing of paint system application

CASE STUDY – Amwell Road Bridge: • 100 Tons of Steel (typical mix sizes/shapes); 25,000 SF • 80 Year Life-Cycle • C3 – Moderately Industrial Environment • 3% Inflation; 4% Interest • Initial Cost & Maintenance Touch-up Painting • 33 Tons for Duplex System (fascia girders only)

Source - American Galvanizers Association (AGA) “Galvanizing Cost” Online Life-Cycle Cost Estimator

AALLTTEERRNNAATTIIVVEESS IINNIITTIIAALL CCOOSSTT LLIIFFEE--CCYYCCLLEE CCOOSSTT

3-Coat Paint System (Entire Bridge) $3.17/ft2 $318,800 A

Hot-Dip Galvanizing* (Entire Bridge) $1.76/ft2 $56,000 B

Duplex System (Entire Bridge) $4.92/ft2 $199,500 C

Duplex System (Fascia Girders Only) $2.82/ft2 $106,600 B & C

A: Maintenance Cycle Years 21, 27, 38, 59, 66, 76 (6 Touch-ups Total) B: Maintenance Cycle Year 72 (1 Touch-up; *Reg. Maintenance Unnecessary) C: Maintenance Cycle Years 46 & 61 (2 Touch-ups Total)

Continue maintenance touch-up painting

Periodically monitor the subject bridge population

Promote the use of self-cleaning bridge details

Determine correlation between structure proximity to water and coating performance

Examine performance of irregular members (gusset plates)

Assess the effect of weld metal

Formulate detailed guidelines for specifying preferred Base Primer and Finish Coat paints

Develop best practices and prepare standard specifications for surface preparation and paint application

Modify Somerset County Special Provisions for paint application

Educate Bridge Owners, Engineers and Inspectors