Federal Highway Administration 

(FHWA) Coatings and Corrosion 

Laboratory (CCL):

Ongoing Research on Corrosion

Office of Infrastructure Research and Development

FHWA CCL 

October 2023

Frank Jalinoos

Coatings and corrosion lab manager

Long-Term Infrastructure Performance Team 

© USchools / iStock.
CCL Coatings and 

Corrosion Laboratory

Outline

► CCL expertise, mission, and research disciplines.

► Stress corrosion cracking (SCC) of stainless steel (SS) in 

contact with chloride ions:

 Phase I—SCC in U-bend specimens.

 Phase II—SCC of SS embedded in chloride-contaminated concrete 

slabs.

 Phase III—long-term performance of SS rebars.

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CCL Coatings and 

Corrosion Laboratory

Turner-Fairbank 

Highway Research 

Center Expertise ► Structural design and performance. ► Pavement design and evaluation. ► Safety design and operations. ► Human factors analytics. ► Connected vehicle technologies. ► Intelligent transportation systems.

Source: FHWA. 3
CCL Coatings and 

Corrosion Laboratory

Laboratories

Safety

Source: FHWA.

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CCL Coatings and 

Corrosion Laboratory

CCL Goals

1. Conduct research to discover innovative solutions for the most critical 

materials-related problems that affect durability and serviceability of 

transportation infrastructure.

2. Focus on research that can yield field-applicable results.

3. Make the Nation’s infrastructure safer and last longer by providing useful

research products to stakeholders (e.g., State and local highway 

agencies, industries, and academia).

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CCL Coatings and 

Corrosion Laboratory

Corrosion Modeling and Simulation

Data sources: 

► Construction 

documents.

► Field assessment.

► Laboratory testing. 

Modeling corrosion:

► Chloride ingress.

► Corrosion initiation and 

propagation.

► Corrosion damage to 

steel and concrete.

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Source: FHWA.

CCL Current Corrosion Research Projects
CCL Coatings and 

Corrosion Laboratory

Recently Completed Corrosion Research Projects

► Report on best practices guidance for corrosion control and 

mitigation (a congressionally mandated study of Federal 

Highway Administration (FHWA) corrosion guidance to 

industry) (Ault and Becker 2019).

► Laboratory evaluation of corrosion resistance of metallic 

dowel bars (Lee 2018b). 

► Laboratory evaluation of corrosion resistance of metallic 

rebar (Lee 2018a).

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CCL Coatings and 

Corrosion Laboratory

Current Corrosion Research Projects

►Stress corrosion cracking (SCC) of stainless steel 

(SS) in contact with chloride ions (SCC of SS 

rebars).

►Corrosion performance of alternative strand 

materials.

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CCL Coatings and 

Corrosion Laboratory

Stress Corrosion Cracking (SCC) of 

Stainless Steel (SS) in Contact With 

Chloride Ions

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CCL Coatings and 

Corrosion Laboratory

Phase I—SS U-Bend Specimens

► Studied SCC in several SS specimens under corrosive

atmospheric conditions.

► Achieved stress in U-bend specimens by deformation.

Source: FHWA.

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CCL Coatings and 

Corrosion Laboratory

Exposure Conditions in Phase I

► SS specimens used were duplex 2205 and 2304, XM-28, 316LN,

and 304L.

► Intent was to simulate initially high pH concrete pore solution and 

deicing salts.

► SS may develop localized corrosion at locations of concentrated

chloride ions at relatively low temperature (around 50 °C/122 °F).

► Specimens were constantly exposed to salts (i.e., calcium 

chloride, magnesium chloride, and sodium chloride) in

evaporative (i.e., including deliquescent) conditions.

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CCL Coatings and 

Corrosion Laboratory

SS U-Bends in Test Chamber

All photos source: FHWA.

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CCL Coatings and 

Corrosion Laboratory

Droplets and Corrosion

1 mm 1 mm

All photos source: FHWA.

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CCL Coatings and 

Corrosion Laboratory

SCC Developed in U-Bend Samples

All photos source: FHWA.

SCC in 316LN SS due to magnesium chloride.

SCC in 304L SS due to calcium chloride.

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CCL Coatings and 

Corrosion Laboratory

Localized Corrosion in XM-28 SS

All photos source: FHWA.

XM-28 in magnesium chloride. XM-28 in sodium chloride.

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CCL Coatings and 

Corrosion Laboratory

SCC in 316LN SS

All photos source: FHWA.

SCC in 316LN SS due to magnesium chloride.

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CCL Coatings and 

Corrosion Laboratory

SCC in 304L SS

200 μm 20 μm

All photos source: FHWA.

SCC in 304L SS due to magnesium chloride.

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CCL Coatings and 

Corrosion Laboratory

No SCC in 2304 SS

All photos source: FHWA.

Microscopic image showing grains of the 2304 SS.

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CCL Coatings and 

Corrosion Laboratory

No SCC in 2205 SS

50 μm

All photos source: FHWA.

Microscopic image showing grains of the 2205 SS.

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CCL Coatings and 

Corrosion Laboratory

Phase II—SCC of SS Embedded in 

Chloride-Contaminated Concrete 

Slabs

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CCL Coatings and 

Corrosion Laboratory

SCC in SS

► SCC is of great concern in SS exposed to aggressive environments. 

The stresses that cause SCC are tensile in nature.

► SCC is not the result of stress concentration at surface flaws caused 

by corrosion reactions.

► Residual stresses and tensile stresses often cause SCC (e.g., rebar 

hooks, welds, tendons, bars, and fasteners). 

► Temperature and chloride ions are critical for SCC in SS. 

► Crack propagation results from the interaction of mechanical stress 

and corrosion reactions.

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CCL Coatings and 

Corrosion Laboratory

SS Reinforcement

The austenitic SS are also considered to be the most weldable of the high-alloy 

steels and can be welded by all fusion and resistance welding processes: 

1. 304L (unified numbering system (UNS) S30403): an austenitic SS with a 

minimum of 18-percent chromium and 8-percent nickel, and the carbon 

maximum is 0.030 percent (ASM International 1990).

2. 316LN (UNS S31653): a nitrogen-alloyed austenitic SS with molybdenum 

(Mo) addition. Due to a lower carbon content, 316LN loses some of its 

strength. It is alloyed with nitrogen to compensate for the loss of strength 

(ASM International 1990).

3. XM-28 (UNS S24100): a high-manganese, low-nickel austenitic SS, 

strengthened by extra nitrogen present in solid solution (ASM International 

1990).

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CCL Coatings and 

Corrosion Laboratory

SS Reinforcement (Continued)

Duplex (austenitic ferritic) SS—better resistance to stress corrosion cracking:

• Alloy 2304 (UNS S32304): usually called a lean duplex SS with 23-percent 

chromium and 4-percent nickel with no Mo content (ASM International 

1990).

• 2205 duplex (UNS S32205): a duplex SS containing high chromium, 

molybdenum, and nitrogen contents (ASM International 1990).

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CCL Coatings and 

Corrosion Laboratory

Steel Specimens

Source: FHWA.

Residual stress is 

induced in SS 

hooks by plastic 

deformation.

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CCL Coatings and 

Corrosion Laboratory

Ponding

Source: FHWA.

Ponding concrete slab with brine solutions.

Brine solutions:

• Sodium chloride (NaCl).

• Calcium chloride 

(CaCl2).

• Magnesium chloride 

(MgCl2).

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CCL Coatings and 

Corrosion Laboratory

Exposure Conditions in Phase II

Source: FHWA.

Ponding and heating cycles:

• Ponding: 4 d.

• Heating: 3 d.

Image caption:

• Left: Specimens were heated 

to 50 °C /122 °F with lamps in 

an insulated box.

• Right: measuring corrosion 

after removal of insulated 

boxes.

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CCL Coatings and 

Corrosion Laboratory

Corrosion Measurements

Source: FHWA.

Polarization resistance measurement with a potentiostat. 

Corrosion measurements:

• Half-cell potential of top 

hooks.

• Macrocell corrosion 

current. 

• Polarization resistance.

• Electrochemical 

impedance 

spectroscopy.

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CCL Coatings and 

Corrosion Laboratory

Phase III—Long-Term Performance of 

SS Rebars 

SS rebars in concrete slabs:

Rebar size: #5 bars.

SS types: (ASM International 1990)

• XM28.

• 316LN.

• 2205.

• 2304.

Control: mild steel black bar. (ASM 

International 1990)

Slab dimension: 3 ft by 4 ft by 1 ft. 

Concrete mix:

• Regular.

• Light-weight aggregate concrete.

Concrete clear cover:

• Top: 2 inches. 

• Bottom: 2.5 inches.

Saltwater concentration: 15-percent NaCl.

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CCL Coatings and 

Corrosion Laboratory

Long-Term Performance of SS Rebars 

(Continued)

Dike

Saltwater

Top view.

Front view. Side view. Bars

All figures source: FHWA.

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CCL Coatings and 

Corrosion Laboratory

CCL Web Page

https://highways.dot.gov/research/laboratories/coatings-corrosion-laboratory/publications (FHWA n.d.)

Google® search: “FHWA Corrosion Lab”

© 2020 Google. 

Search FHWA site

Explore Research and 

Technology

Coatings and Corrosion 

Laboratory Overview

Laboratories Overview

Projects

Publications

Source: FHWA (FHWA n.d.). 

.

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CCL Coatings and 

Corrosion Laboratory

References

Ault, J. P., and D. R. Becker. 2019. Report on Best Practices Guidance for Corrosion Control and Mitigation, as 

requested by the House Report 115-237. Washington, DC: Federal Highway Administration.

ASM International. 1990. ASM Handbook. Volume 1, Properties and Selection: Irons, Steels, and HighPerformance Alloys. Prepared under the direction of the ASM International Handbook Committees.. Materials 

Park, OH :ASM International.

FHWA. n.d. “Corrosion and Publications.” (web page). https://highways.dot.gov/research/laboratories/coatingscorrosion-laboratory/corrosion-coating-publications, last accessed October 21, 2021.

Lee, S.-K. 2018a. A Comparative Laboratory Study of Metallic Reinforcing Steels for Corrosion Protection of 

Reinforced Concrete Bridge Structures. FHWA-HRT-15-078. Washington, DC: Federal Highway Administration.

Lee, S.-K. 2018b. Laboratory Evaluation of Corrosion Resistance of Various Metallic Dowel Bars. FHWA-HRT15-079. Washington, DC: Federal Highway Administration.

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© Peeterv / iStock.

CCL Coatings and 

Corrosion Laboratory

Contact

Frank Jalinoos

frank.jalinoos@dot.gov

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CCL Coatings and 

Corrosion Laboratory

Disclaimer

The U.S. Government does not endorse products or manufacturers. Trademarks 

or manufacturers’ names appear in this presentation only because they are 

considered essential to the objective of the presentation. They are included for 

informational purposes only and are not intended to reflect a preference, 

approval, or endorsement of any one product or entity.

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