Introduction to fhwa coatings studies (trb 2009)

TURNER-FAIRBANK HIGHWAY RESEARCH CENTERTURNER-FAIRBANK HIGHWAY RESEARCH CENTER
One-Coat Systems Applicable to
Steel Bridge Structures
Coatings & Corrosion Laboratory
Office of Infrastructure R & D
Turner-Fairbank Highway Research Center
Federal Highway Administration
McLean, VA 22101
TRB 2009
One-Coat Systems Applicable to
Steel Bridge Structures
McLean, VA 22101
TRB 2009

Coating SystemsCoating Systems
1. 3-coat control (Organic Zn + Epoxy + Polyurethane)
2. 2-coat control (MCU-Zn + Polyaspartic)
3. Polyaspartic (ASP)
4. Epoxy Mastic (EM)
5. Calcium Sulfonate Alkyd (CSA)
6. Glass Flake Polyester (GFP)
7. High Build Acrylic (HBAC)
8. Waterborne Epoxy (WBEP)
9. Polysiloxane (SLX)
10. Urethane Mastic (UM)

Test PanelsTest Panels
Unscribed Scribed Unscribed Scribed Unscribed Scribed
1 3-coat 3 3 3 3 6 6 24
2 2-coat 3 3 3 3 6 6 24
3 ASP 3 3 3 3 6 6 24
4 EM 3 3 3 3 6 6 24
5 CSA 3 3 3 3 6 6 24
6 GFP 3 3 6**
7 HBAC 3 3 3 3 6 6 24
8 WBEP 3 3 3 3 6 6 24
9 SLX 3 3 3 3 6 6 24
10 UM 3 3 3 3 6 6 24
30 30 27 27 54 54 222
Outdoor Weathering (6 x 12 in.)*
Total
** Only laboratory test panels were prepared due to late arrival of test material.
Total
* The test panels will be exposed to natural weathering at Turner-Fairbank facility with periodic salt spray.
System
No.
System ID
Laboratory (4 x 6 in.) Sea Isle (4 x 6 in.)

Accelerated Laboratory TestingAccelerated Laboratory Testing
1. Freeze Cycle for 24 hours at -23 oC (-10 oF)
2. UV/Condensation Cycle for 168 hours:
• 4-hour UV at 60 oC (140 oF)
• 4-hour condensation at 40 oC (104 oF)
3. Alternating Salt-Fog Cycle for 168 hours:
• 1-hour wet with 0.35% (NH4)2SO4 plus 0.05% NaCl solution at
ambient temperature
• 1-hour dry at 35 oC (95 oF)

Accelerated Laboratory Testing - ContinuedAccelerated Laboratory Testing - Continued
● Test Hours per Cycle: 360 Hours
● Total Test Cycles: 19
● Total Test Hours: 6,840 Hours
● Performance Evaluation After Each Test Cycle

Outdoor Exposure at TFHRCOutdoor Exposure at TFHRC
• Periodic performance evaluation every six months

Outdoor Exposure at Sea Isle City, NJOutdoor Exposure at Sea Isle City, NJ
• Periodic performance evaluation every six months

Periodic Performance EvaluationPeriodic Performance Evaluation
1. Surface Defects and Failures ( By holiday detector and digital
microscope )
2. Coating Impedance Properties
3. Rust Creepage (ASTM D7087)
4. Photographic Documentation
5. Change of Gloss *
* For outdoor exposed panels only

PhotomicrographsPhotomicrographs
(2-coat system, 20X) (3-coat system, 20X)

Rust Creepage Growth (Lab Testing)Rust Creepage Growth (Lab Testing)
0
5
10
15
20
25
30
35
40
0 720 1440 2160 2880 3600 4320 5040 5760 6480 7200
Duration (hour)
Creepage(mm)
3-coat
2-coat
ASP
EM
CSA
GFP
HBAC
WBEP
SLX
UM

Rust Creepage Growth (Sea Isle City)Rust Creepage Growth (Sea Isle City)
0
5
10
15
20
25
30
35
40
0 4320 8640 12960 17280
Duration (hour)
Creepage(mm)
3-coat
2-coat
ASP
EM
CSA
HBAC
WBEP
SLX
UM
0.0
0.5
1.0
1.5
12240 12960
0.0
0.5
1.0
1.5
12240 12960
0.0
0.5
1.0
1.5
12240
0.0
0.5
1.0
1.5
12240 12960
0
5
10
15
20
25
30
35
40
0 4320 8640 12960 17280
Duration (hour)
Creepage(mm)
3-coat
2-coat
ASP
EM
CSA
HBAC
WBEP
SLX
UM
0.0
0.5
1.0
1.5
12240 12960
0.0
0.5
1.0
1.5
12240 12960
0.0
0.5
1.0
1.5
12240
0.0
0.5
1.0
1.5
12240 12960

3-Coat System (Control)3-Coat System (Control)
0 2,160 4,320 6,840

CSACSA
0 2,160 4,320 6,840

GFPGFP
0 2,160 4,320 6,840

EMEM
0 2,160 4,320 6,840

WBEPWBEP
0 2,160 4,320 6,840

UMUM
0 2,160 4,320 6,840

FindingsFindings
1. Two control coating systems (3-coat and 2-coat) had a
dry film thickness (DFT) of approximately 13 mils and a
pencil scratch hardness of HB.
2. The 3-coat demonstrated very good performance in
almost all aspects and slightly better than the 2-coat.

Findings - ContinuedFindings - Continued
3. With regard to initial DFT, pencil scratch hardness, and
adhesion properties, the eight one-coat systems varied
significantly compared to those of the controls.
4. Four one-coat systems (ASP, WBEP, SLX, and UM)
had either higher adhesion strength or thicker DFT
compared to the controls, but their performance in terms
of defect development, rust creepage, and rate of
physical deterioration was far inferior to the rest.

5. The fifth one-coat system, HBAC, had a DFT of 10.4
mils with a very soft pencil scratch hardness (6B) and
showed mixed results with a relatively low number of
coating defects, moderate rust creepage resistance,
and good physical appearance.

6. To date, CSA has been the best performer despite its
softness and very weak adhesion strength.
7. GFP is also an excellent coating system and is the 2nd
best in the overall performance rating. These two one-
coat systems outperformed the controls.
8. Performance of EM was comparable to those of the
control systems.

100-Year Life Coating Systems
McLean, VA 22101
TRB 2009
100-Year Life Coating Systems
McLean, VA 22101
TRB 2009

BackgroundBackground
1. This is a Congress mandated study under the HPS
program.
2. Main objective is to identify and evaluate coating
materials that can provide 100 years of maintenance-
free service life for steel bridge structures.
3. This study started in November 2008 and will be
carried out for 36 months.
4. Some types of weathering steel will be also tested.

Coating Systems SelectedCoating Systems Selected
System
Number
Category Generic Coating Name
1 Control - Conventional 3-coat Shop System IOZ / Epoxy / Aliphatic Polyurethane
2 Control -3-coat OZ Shop System Zn-rich Epoxy / Epoxy / Aliphatic Polyurethane
3 3-coat Fluoro-Topcoat System MCU Zn / Epoxy / Fluorourethane
4 2-coat Fast Dry Coating Zn-rich Epoxy / Aliphatic Polyurethane
5 2-coat Polysiloxane Inorganic Zinc / Polysiloxane
6 Metallizing (conventional) + Topcoat Thermal Sprayed Zinc / Linear Epoxy
7 Organic Zinc Rich Epoxy (Zinc Flake)/Linear Epoxy Experimental Primer / Topcoat
8 Calcium Sulfonate Alkyd HR Single Coat CSA

Type 1 Test Panels (4 x 6 in.)Type 1 Test Panels (4 x 6 in.)
Accelerated Lab
Test
Outdoor Weathering
Test
Destructive Test
(Ahesion)
Control 2 10 10 4 24
Others 6 30 30 12 72
Subtotal 8 40 40 16 96
Number of Test Panels
Number of
Coating
Systems
Category
Total Number
of Test
Panels

Type 2 Test Panels (18 x 18 in.)Type 2 Test Panels (18 x 18 in.)
Outdoor Weathering
Test (without salt
spray)
Outdoor Weathering
Test (with salt spray)
Outdoor
Weathering Test
(Golden Gate Bridge)
Control 2 2 2 2 6
Others 6 6 6 6 18
Subtotal 8 8 8 8 24
Number of Test Panels
Number of
Coating
Systems
Category
Total Number
of Test
Panels

[A-A] [B-B]
18 in.
18 in.
B
B
A
A
Stripe
Coat
Weld
Normal Test Area
with Attachments
(No Cl-, target
anchor profile,
target DFT)
Poorly Prepared
Area (4 x 8 in.)
(Cl-, less anchor
profile, 20% less
DFT)
20% Thicker DFT
Area (4 x 8 in.)
(No Cl-, target
anchor profile)
Tee
Angle
Angle
Bolt & nut Angle
FHWA Outdoor Large-Scale Weathering Test Panel for 100-Year Coating Study

Test PanelsTest Panels

TestsTests
1. Coating Thickness
2. Gloss
3. Color
4. Pencil Scratch Hardness
5. Infrared Spectrometry
6. Adhesion
7. EIS
8. Rust Creepage
9. Surface Examination
(Defects & Other
Types of Failures)
10. Digital Microscopy
11. Digital Photography

Future Research Ideas (Some Thoughts)Future Research Ideas (Some Thoughts)
1. Chloride Tolerance on Various Steel Substrate Conditions
• Test Methods – Accuracy and New Methods
• Threshold Values – 7 µg/cm2 (?)
2. Field Coating Performance Monitoring Devices
• Thermography
• Sensors, etc.
3. Protective Barrier Systems for Concrete Bridge Structures
• Waterproofing Membranes for Bridge Decks
• Traditional Coating Systems
4. Signage and Pavement Markings

EIS Test Cells for Field MonitoringEIS Test Cells for Field Monitoring

Introduction to fhwa coatings studies (trb 2009)

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