TECHBRIEF Multiple Corrosion-Protection 

Systems for Reinforced 

Concrete Bridge Components

FHWA Publication No: FHWA-HRT-11-059

FHWA Contact: Paul Virmani, HRDI-60, (202) 493–3052, paul.

virmani@dot.gov

This is a summary of a Federal Highway Administration (FHWA) 

project that is fully documented in a separate report under the 

same title (FHWA-HRT-11-060).

Introduction

Epoxy-coated reinforcement (ECR) is the principal concrete 

reinforcing material currently in use in corrosive environments 

in the United States. The purpose of this study was to evaluate 

methods for making ECR more corrosion resistant by using 

multiple corrosion-protection strategies in bridge decks and bridge 

members in marine environments where salt, moisture, and high 

temperatures are prevalent.

The research was conducted using laboratory and large field test 

specimens, and the results were used to compare the performance 

of the corrosion-protection systems on the basis of chloride 

threshold, corrosion rate, life expectancy, and cost effectiveness. 

Fusion-bonded thermoset ECR was evaluated in conjunction with 

inorganic and organic corrosion inhibitors, bars coated with zinc 

prior to the application of epoxy, and chemical pretreatments 

and epoxy formulations that increase the adhesion of the epoxy 

coating to the reinforcing steel.

Approach

Corrosion-Protection Systems

This study evaluated 11 systems in which ECR was combined 

with another corrosion-protection system and 3 systems in 

which uncoated steel was combined with a corrosion inhibitor. 

The research included seven bar types: one uncoated and six 

with a fusion-bonded epoxy coating. Uncoated conventional 

reinforcing steel and conventional ECR served as the controls. 

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.tfhrc.gov
2

The multiple corrosion-protection systems 

included the following: 

• Conventional ECR used in conjunction with 

one of three corrosion inhibitors: calcium 

nitrite (designated DCI) and two organic 

inhibitors (Rheocrete® 222+

 and HycreteTM, 

designated RH and HY, respectively).

• Bars treated with a primer coating containing 

microencapsulated calcium nitrite prior to 

coating with conventional epoxy.

• Bars with improved adhesion between the 

epoxy and the reinforcing steel (obtained 

through the use of either a zinc chromate 

pretreatment or one of two special epoxies 

designed to provide greater adhesion).

• The combination of bars coated with an 

improved adhesion epoxy and the addition of 

calcium nitrite to the mortar or concrete used 

in the tests. 

• Bars with multiple coatings consisting of 

a 2-mil (50-μm) layer of 98 percent zinc and 

2 percent aluminum that were, in turn, coated 

with a conventional epoxy. 

Test Parameters and Conditions

Before corrosion testing, the researchers evaluated the bars for coating thickness and number 

of holidays (i.e., microscopic holes through the 

coating). The bars were also evaluated for coating 

adhesion using the cathodic disbondment test. All 

bars met the requirements of ASTM A775 for coating thickness, except the bars coated with calcium 

nitrite primer.(1) Those bars tended to have larger 

percentages of coating measurements below 

7 and 5 mils (175 and 125 μm) than the maximum 

allowable values of 10 and 5 percent, respectively. 

Only the bars coated with the calcium nitrite 

primer exhibited holidays, although the number 

of holidays was below the maximum allowable of 

three holidays per meter. In the cathodic disbondment test, the average coating disbondment radius 

for the conventional ECR and one of the highadhesion epoxy-coated bars was above 0.16 inches 

(4 mm), the maximum allowed by ASTM A775 when 

qualifying an epoxy.(1) However, the performance 

of the bars in the cathodic disbondment tests was 

not proven to be a predictor of performance in the 

corrosion tests.

The corrosion tests included rapid macrocell, 

bench-scale, and field tests. Specimens were 

autopsied at the completion of testing. In the benchscale tests, concretes with water-cement ratios of 

0.45 and 0.35 were used to evaluate some systems. 

In all tests, the epoxy coating was penetrated by 

0.125-inch (3.2-mm)-diameter holes to simulate 

damage that occurs during construction.

Specimen Type and Exposure Regimes

The rapid macrocell test specimen consisted of 

either a bare reinforcing bar or a bar clad in mortar 

(mortar-wrapped). The contact surface between the 

mortar and the bar simulated the contact obtained 

between concrete and reinforcing bars in structures through the use of realistic water-cement and 

sand-cement ratios. Bars representing the anode 

and cathode were placed in separate containers. 

At the anode, the bars were surrounded by a 

simulated concrete pore solution containing a preselected concentration of sodium chloride, while 

the bars at the cathode were surrounded by the 

simulated concrete pore solution alone. The two 

containers were connected by a salt bridge (for ion 

transfer), and the test specimens were electrically 

connected across a single 10-ohm resistor. The 

voltage drop across the resistor was measured to 

determine the macrocell corrosion current, which 

was used to calculate the thickness loss of the 

metal. The specimens were also monitored for the 

open-circuit corrosion potential of the bars.

Bench-scale tests included southern exposure and 

cracked beam tests. Both tests consisted of small 

slabs of concrete containing two mats (top and 

bottom) of reinforcing steel that were electrically 

connected across a 10-ohm resistor. A simulated 

12-mil (0.3-mm)-wide crack was placed parallel to 

and above the top reinforcing bars using a stainless 

steel shim during fabrication of the cracked beam 

specimens. The shim was removed shortly after the 

concrete set. The southern exposure test specimens 

had no cracks. For both bench-scale tests, the slabs 

were subjected to a 7-day alternate ponding and 
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drying regime, with ponding at 73 ± 3 °F (23 ± 2 °C) 

for 4 days and drying at 100 °F (38 °C) for 3 days. 

Prior to drying, the solution was removed from 

the upper surface. The ponding and drying regime 

continued for 12 weeks. Then, the specimens were 

subjected to continuous ponding for 12 weeks 

at 73 ± 3 °F (23  ±  2 °C), after which the alternate 

ponding and drying regime began again. The two 

regimes continued for 96 weeks. The specimens 

were monitored for macrocell corrosion current 

and corrosion potential. Selected bench-scale 

specimens were also monitored for total corrosion 

current using the linear polarization resistance test.

Field test specimens consisted of concrete slabs 

with two mats of reinforcing bars that represented 

bridge decks but had a 1-inch (25-mm) cover to 

shorten the time to corrosion initiation. The field test 

was designed to obtain a measure of the performance of corrosion-protection systems under 

realistic exposure conditions. Like the bench-scale 

specimens, some field test specimens were 

uncracked and some had simulated cracks directly 

above and parallel to select reinforcing bars. A dam 

made of weatherstripping was attached to the upper 

concrete surface to hold a salt solution that was 

ponded on the specimens every 4 weeks. Corrosion 

measurements were obtained for a minimum of 

250 weeks. Salt was applied to the specimens at the 

same annual rate used for bridge decks in Kansas. 

Results

The test results indicate that the corrosion losses 

on the damaged areas on ECR (all systems) were 

generally higher than but of a similar magnitude to 

the average corrosion losses exhibited by uncoated 

conventional reinforcing steel. The relatively higher 

losses on the damaged areas may be because the 

losses recorded for uncoated conventional steel 

represent values that are averaged over the full 

contact surface, all of which may not be corroding. 

Superior performance was observed over the 

15-week test period for the mortar-wrapped 

macrocell specimens containing ECR. These results 

are in concert with the results for epoxy-coated 

bars in the bench-scale tests, which indicate 

that, due to the natural variation in chloride 

concentration within concrete, all damaged areas 

on ECR do not come in contact with high chloride 

contents at the same time. When uncoated steel 

was used, however, a portion of the unprotected 

steel is expected to undergo corrosion. As a result, 

a higher average chloride content was required to 

initiate corrosion in ECR with a damaged coating 

than for uncoated conventional reinforcement. 

In terms of overall performance, the use of 

concrete with a lower water-cement ratio provided 

an advantage for both uncoated and coated 

reinforcement in uncracked concrete due to its role 

in delaying penetration of chlorides and limiting 

access of oxygen and moisture to the steel. The 

same advantage was not apparent in all cases for 

cracked concrete. Concrete with a lower watercement ratio resulted in a lower corrosion rate for 

uncoated steel but not for damaged ECR. 

As observed in other studies, increasing the 

adhesion between the epoxy coating and 

reinforcing steel did not provide an advantage 

over conventional ECR.(2) 

In uncracked concrete, the use of corrosion 

inhibitors and the use of the primer coating 

containing calcium nitrite provided added 

protection for damaged ECR. In general, the lower 

the water-cement ratio, the better the protection. 

Of the systems incorporating a corrosion inhibitor, 

bars with the calcium nitrite primer coating 

under the epoxy coating and conventional ECR 

cast in concrete with one of the organic inhibitors 

(specifically, HY) provided improved performance, 

although the relative advantages were lower for 

cracked concrete than for uncracked concrete. 

The test results for the bars with multiple (zincepoxy) coatings indicate that the zinc helped to 

protect the underlying conventional steel. This 

protection, however, was obtained through the 

sacrificial loss of zinc. The multiple-coated bars 

exhibited relatively high corrosion rates compared 

to conventional ECR in the bench-scale tests but 

performed in a similar manner to conventional 

ECR in the field tests in both uncracked and 

cracked concrete.

The test data were combined with chloride 

measurements on bridges in Kansas to evaluate 
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the systems’ life expectancy and cost effectiveness, 

expressed in terms of time to first repair and the 

present value of initial construction and repair 

costs over a 75-year design life. Comparisons 

were based on a bridge with a 150-ft (46-m) span 

and 36-ft (11-m) width. The deck thickness was 

8.5 inches (219 mm). Calculations were based on a 

75-year economic life using costs from Kansas and 

South Dakota. 

Data analysis for time to first repair for the 

11  systems evaluated in this study is shown in 

figure  1. All of the systems incorporating ECR 

provided a longer time to first repair than the 

systems incorporating conventional reinforcement. Conventional reinforcement without a 

corrosion inhibitor provided the shortest time to 

first repair, approximately 17 years. The time to 

first repair progressively increases with the addition of organic corrosion inhibitor RH, DCI, and 

organic corrosion inhibitor HY. The bridges with 

systems incorporating uncoated bars required two 

or three repairs during a 75-year design life. In 

contrast, the systems incorporating coated reinforcement required a single repair over 75 years. 

Of the epoxy-coated systems, conventional ECR, 

along with the three systems providing increased 

adhesion between the epoxy and the steel and one 

system with an organic inhibitor (specifically, RH) 

provided nearly identical predicted times to first 

repair (55 years). The other systems, DCI, organic 

corrosion inhibitor HY, the bars with the calcium 

nitrite primer coating under conventional epoxy, 

and the multiple-coated bars, provided somewhat 

longer predicted times to first repair at 64, 58, 64, 

and 56 years, respectively. As shown in figure 2, 

the costs over 75 years for the systems incorporating conventional reinforcement were higher than 

those containing ECR, and the costs for the individual systems incorporating ECR were similar.

Conclusions

The following conclusions were reached as a 

result of this study:

• Conventional fusion-bonded epoxy coatings 

significantly improve the corrosion resistance, 

life expectancy, and cost effectiveness of 

reinforcing steel in severe climates, such as in 

the case of bridge decks requiring application 

of deicing chemicals.

• Coated bars with damaged coatings initiate 

corrosion at chloride contents within concrete 

0

15

30

45

60

75

Time to First Repair (years)

Figure 1. Time to first repair.
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that are several times greater and corrode 

at rates that are typically two orders of magnitude below those exhibited by conventional 

reinforcement. 

• Limited additional protection and extension of 

time to first repair are achieved using bars with 

a primer coating containing microencapsulated 

calcium nitrite underneath a conventional 

epoxy coating, multiple-coated bars with a 

2-mil (50-μm) coating of 98 percent zinc and 2 

percent aluminum underneath a conventional 

epoxy coating, and concrete containing the 

corrosion inhibitors DCI and HY. The differences 

in costs over a 75-year design life are relatively 

small for coated bars. Concrete containing 

HY may exhibit lower compressive strength 

and reduced resistance to surface scaling 

compared to concretes with other inhibitors 

or without an inhibitor unless modified, such 

as through an increase in cement content. 

As a result, additional research is required to 

establish criteria that will preclude a loss of 

durability when HY is used.

• Conventional reinforcement in concrete 

containing a corrosion inhibitor has a longer 

service life and is more cost effective than 

conventional reinforcement in concrete 

without a corrosion inhibitor but has a shorter 

service life and is less cost effective than any 

of the coated-bar systems evaluated.

• Cracks in concrete directly over and parallel 

to the reinforcement, such as those found 

in bridge decks, result in earlier corrosion 

initiation and higher corrosion rates than 

obtained with intact concrete for all systems.

• Epoxies that provide initially high adhesion to 

the underlying steel provide no advantage in 

terms of improved corrosion performance or 

improved adhesion when used in concrete. 

• Using concrete with a reduced water-cement 

ratio lowers the corrosion rate for both 

conventional reinforcement and ECR under all 

conditions in intact concrete but provides only 

limited corrosion protection when cracks allow 

direct access of chlorides to reinforcing bars. 

• Corrosion inhibitors consistently provide 

improved corrosion protection when used in 

conjunction with conventional reinforcement 

and ECR in intact concrete but do so to a lesser 

degree in cracked concrete. 

$0

$100

$200

$300

$400

$500

$600

$700

$800

Present Cost ($/m2

)

1 m2 = 10.8 ft2

Figure 2. Present cost for initial construction and repair over 75 years.
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Researchers—This study was performed by the University of Kansas Center for Research, Inc., 

2385 Irving Hill Road, Lawrence, KS, 66045-7563, (785) 864-3441. 

Distribution—This TechBrief is being distributed according to a standard distribution. Direct 

distribution is being made to the Divisions and Resource Center.

Availability—This TechBrief may be obtained from the FHWA Product Distribution Center by email to 

report.center@dot.gov, fax to (301) 577-1421, phone to (301) 577-0818, or online at http://www.fhwa.dot.

gov/research.

Key Words—Adhesion, Chlorides, Concrete, Corrosion, Corrosion inhibitor, Durability, Epoxy-coated 

steel, Zinc-coated steel.

Notice—This document is disseminated under the sponsorship of the U.S. Department of 

Transportation in the interest of information exchange. The U.S. Government assumes no liability 

for the use of the information contained in this document. The U.S. Government does not endorse 

products or manufacturers. Trademarks or manufacturers’ names appear in this report only because 

they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides highquality information to serve Government, industry, and the public in a manner that promotes public 

understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, 

and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and 

processes to ensure continuous quality improvement.

August 2011 FHWA-HRT-11-059

HRDI-60/08-11(600)E

• Corrosion inhibitors have a greater relative effect 

on uncoated than on coated reinforcement. 

• Reinforcement with multiple coatings consisting of 98 percent zinc, 2 percent aluminum, 

and conventional epoxy exhibits high corrosion rates in cases where the concrete is often 

wet but exhibits corrosion rates similar to those 

exhibited by conventional ECR under conditions 

similar to those in bridge decks. The metallic 

coating corrodes in preference to the underlying steel, providing some additional protection. 

• All coated bars that were evaluated exhibited corrosion losses at openings through the 

coating. A reduction in adhesion between an 

epoxy coating and the reinforcing steel occurs 

after a period of exposure to corrosive conditions. This reduction increases with increasing chloride content in the concrete and in the 

presence of cracks and decreases with the use 

of corrosion inhibitors, the use of multiplecoated reinforcement, and the use of electrical 

isolation of the epoxy-coated bars from each 

other. Corrosion products form under the coating where adhesion has been reduced. 

• For periods up to 5 years under exposure 

conditions representative of those in bridge 

decks, the reduction in adhesion between an 

epoxy coating and the reinforcing steel did not 

affect the rate at which coated bars corrode. 

References

1. ASTM A775/A775M-04a (2004). “Standard 

Specification for Epoxy-Coated Steel Reinforcing Bars,” ASTM International, West 

Conshohocken, PA.

2. McDonald, D.B., Pfeifer, D.W., and Sherman, 

M.R. (1998). Corrosion Evaluation of EpoxyCoated, Metallic Clad, and Solid Metallic 

Reinforcing Bars in Concrete, Report No. 

FHWA-RD-98-153, Federal Highway Administration, Washington, DC.