CORROSION OF STEEL GIRDER BRIDGE ANCHOR BOLTSdocs.trb.org/prp/09-2517.pdf · Moser, Lindquist...

CORROSION OF STEEL GIRDER BRIDGE ANCHOR BOLTS By Robert D. Moser (corresponding author) Georgia Institute of Technology 790 Atlantic Drive Atlanta, GA 30332 Phone: (706) 835-5526 Fax: (404) 894-2278 Email: [email protected] Lisa J. Lindquist Hoeke Georgia Institute of Technology 790 Atlantic Drive Atlanta, GA 30332 Phone: (412) 716-7237 Fax: (404) 894-2278 Email: [email protected] Preet M. Singh Georgia Institute of Technology 500 10th Street, N. W. Atlanta, GA 30332 Phone: (404) 894-6641 Fax: (404) 894-4778 Email: [email protected] Lawrence F. Kahn Georgia Institute of Technology 790 Atlantic Drive Atlanta, GA 30332 Phone: (404) 894-8021 Fax: (404) 894-2278 Email: [email protected] Kimberly E. Kurtis Georgia Institute of Technology 790 Atlantic Drive Atlanta, GA 30332 Phone: (404) 385-0825 Fax: (404) 894-2278 Email: [email protected] Word Count: 4,320 + 10*250 (10 Figures and 1 Table) = 6,820 November 15, 2008

TRB 2009 Annual Meeting CD-ROM Paper revised from original submittal.

Moser, Lindquist Hoeke, Singh, Kahn, Kurtis 2

ABSTRACT Corrosion of anchor bolts has been revealed by inspections of steel girder bridges throughout the State of Georgia. Of Georgia’s steel girder bridges, 411 (27%) were found to be experiencing anchor bolt corrosion, with a median age of 39 years when corrosion was first reported. From field investigations of bridges built prior to 1990, A36 carbon steel anchor bolt corrosion is attributed to the formation of corrosion macrocells with the bolt’s concrete embedment and the buildup of dirt and debris at the bearing site. In bridges built post-1990, Type 304 stainless steel anchor bolts may be susceptible to galvanic coupling and localized forms of corrosion. By laboratory based experimentation, it was concluded that A36 carbon steel bearing components may experience active corrosion, with accelerated corrosion rates due to macrocell and galvanic coupling effects in an exposed pH 7.5 environment. It is noted that galvanic coupling may occur on Type 304 stainless steel anchor bolts, but further research is necessary. Type 304, 316, 2101, and 2205 stainless steels were tested for localized corrosion. Only Type 304 stainless steel exhibited localized corrosion when polarized to potentials much higher than anticipated in the Georgia bearing environment. Therefore, it may be concluded that each of the candidate alloys tested is acceptable for use as anchor bolts in Georgia. However, special consideration should be given to the use of Type 304 stainless steel in more aggressive environments, such as industrial settings or regions where deicing salts/chemicals are used frequently.



INTRODUCTION Inspections of steel girder bridges throughout the State of Georgia have revealed a widespread problem: corrosion of the anchor bolts used to fasten the steel girders to the concrete pier caps and abutments (1). Corrosion of anchor bolts can result in eventual loss of lateral load resistance capacity of the bridge and/or the failure of bridge bearing components (2). Bearing Functionality and Durability Requirements A bridge bearing’s primary function is to transfer loads placed on the superstructure into the substructure. Superstructure loads can be both vertical (e.g. dead and live loads) and lateral (e.g. vehicle impacts, wind, and seismic loads). In addition to transferring superstructure forces, bearings must also allow for rotational and translational movements. Movements are caused by temperature change, vibrations, support settlement, and intermittent loadings (3). In order for a bearing to function as designed, it must not degrade over its intended design life of 75-100+ years in current bridges (4).

Anchor bolt corrosion typically results in two types of bearing degradation. First, lateral load resistance capacity is degraded by a loss of bolt cross section due to corrosion, resulting in decreased shear strength. Second, loss of longitudinal sliding ability is caused by the buildup of corrosion products. The buildup of corrosion products in bearings, especially in the slots of expansion bearings or between sliding plates in plate bearings, results in a loss of bearing functionality due to increased friction and failure of bearing components (2). In addition, the seizing of bearing systems can result in the failure of other substructure elements, such as bents and abutments, due to unanticipated thermally induced forces in the bridge. Research Objectives and Approach The goals of this research were to explicitly define the anchor bolt corrosion problem present in Georgia, to research solutions to the problem, to determine if the new anchor bolt design using Type 304 stainless steel bolts is adequate, and to recommend action to the Georgia Department of Transportation to abate anchor bolt corrosion.

Georgia Department of Transportation (GDOT) design standards, maintenance procedures, and bridge inspection reports were reviewed and data compiled. Field investigations and forensic analyses were performed on eight bridges around Georgia. Laboratory testing was performed to confirm the proposed corrosion mechanisms, and to test potential new candidate materials for anchor bolts. STEEL GIRDER BRIDGE BEARING MATERIALS AND DESIGN IN GEORGIA Steel girders bridges in Georgia built prior to 1990 utilized steel sliding plates with painted A36 carbon steel anchor bolts. Following 1990, Type 304 stainless steel anchor bolts were used for steel girder bridge bearing systems. In both cases, anchor bolts are typically 1¼” (3.18cm) diameter x 18” (45.72cm) long swedged rods embedded in concrete (or grouted in drilled holes). For fixed bearings, a 17/16” hole is drilled through both the bearing plates and the girder flange. In expansion bearings, this hole is extended with a 2½” (6.35cm) to 3” (7.62cm) slot depending upon thermal movement requirements (5). Sole plates may be used, and are typically A36 carbon



steel and are welded to the bottom of the girder flange. A36 carbon steel base plates are placed on the surface of the concrete pier cap or abutment. The typical bearing detail is shown in Figure 1 below.

FIGURE 1 Typical Steel Girder Bridge Bearing System Under Investigation GEORGIA STATEWIDE CONDITION ASSESSMENT In an effort to determine the current state of steel girder bridge bearings in Georgia, GDOT inspection reports were reviewed. Of the 1500 steel girder bridges in Georgia, 411 (27%) were judged to be experiencing anchor bolt corrosion (1). All of the bridges with reported anchor bolt corrosion utilized for this assessment were built before Type 304 stainless steel was specified. Thus all reported anchor bolt corrosion documented in this analysis pertains to A36 carbon steel anchor bolts. Three regions of Georgia, Northern, Southern, and Coastal, were examined for their influence on the occurrence of anchor bolt corrosion. Northern and Coastal Georgia are regions were increased chloride presence is anticipated due to the use of deicing salts/chemicals and marine exposure. However, no correlation could be made between anchor bolt corrosion and a bridge’s regional location; that is, the presence of chlorides was not statistically influential. Figure 2 demonstrates that anchor bolt corrosion is consistent throughout Georgia, with 27% to 29% of bridges affected. The median age when anchor bolt corrosion was first indicated in bridge inspection reports was found to be 39 years (1). It is noted that the A36 carbon steel anchor bolts satisfied the design life of older bridges; although extended service is now required.

Concrete Pier Cap or Abutment

Swedged Anchor Bolt Embedded in Concrete

Hole or Slot in Girder Flange

Steel Bridge Girder

Steel Baseplate



FIGURE 2 Regional Anchor Bolt Corrosion Assessment FIELD INVESTIGATION AND FORENSIC ANALYSIS In order to determine the corrosion mechanisms present in bearings, eight bridges were inspected from across the state. At each bridge site attempts were made to inspect both fixed and expansion bearings. Anchor bolts and dirt samples (from the drilled hole in the steel flange and adjacent to the bearing) were removed if possible.

Approximately 40% of the anchor bolts inspected displayed corrosion related section loss (1). Typical diameter losses of approximately 50% were found, with severe cases where the anchor bolt had completely corroded away. Figures 3 and 4 depict a typical and severe case of corrosion. It should be noted that holes in the flanges shown in Figures 3 and 4 were filled with dirt and water which was removed to take photographs of the corroded portion of the anchor bolt.

The observed anchor bolt corrosion consisted of severe necking at the concrete interface with little corrosion of the upper portion of the bolt where no electrolyte was present. This behavior was ubiquitous at the bridges inspected. Based on the maintenance reports, dirt samples, and bridge inspections, it was concluded that environmental effects such as chloride concentration did not significantly affect anchor bolt corrosion.



FIGURE 3 Typical Case of Anchor Bolt Corrosion

FIGURE 4 Severe Case of Anchor Bolt Corrosion Proposed Anchor Bolt Corrosion Mechanisms From the degradation observed during the field investigation and the bearing design used by the GDOT, the following relevant corrosion mechanisms were considered further: macrocell formation resulting in accelerated localized corrosion in pre-1990 bridges, and galvanic coupling and localized corrosion, such as pitting, in post-1990 bridges. Pre-1990 Bridges – Corrosion Macrocell For anchor bolts, part of the bolt is embedded into an alkaline concrete pore solution with a pH of 12-13, which causes the formation of a protective passive film, while the upper portion of the bolt is exposed to dirt, debris, and rain water with a neutral pH of approximately 7. With these effects combined, the upper exposed portion of the anchor bolt acts as an active anodic site, while the embedded portion of the bolt acts as a passive cathodic site – resulting in the formation of a corrosion macrocell and the localized corrosion induced necking observed during bridge inspections, as evidenced in Figures 3 and 4.



It should be noted that the morphology of the macrocell present is complex. Anode-to-cathode area ratios are difficult to estimate, as the system exhibits high ohmic resistance. Therefore, it can be assumed that only a portion of the bolt’s embedment participates in corrosion reactions, and only a certain height of the exposed portion of the bolt is able to react due to low electrolytic conductivity as the bolt projects above the saturated dirt and debris present at the bearing site. Post-1990 Bridges – Galvanic Coupling and Localized Corrosion The post-1990 bearing system specified by the GDOT utilizes Type 304 stainless steel anchor bolts with A36 carbon steel sole and base plates. Therefore, concern for corrosion induced by galvanic coupling should be considered. Galvanic coupling may occur in exposed regions where pH is approximately 7 and contact is made between Type 304 and A36 bearing components in the presence of an ionically conductive electrolyte.

In addition, localized forms of corrosion such as pitting may occur on Type 304 stainless steel anchor bolts and on new candidate alloys and warrants further investigation. EXPERIMENTAL PROGRAM Several laboratory tests were conducted to determine the corrosion behavior of anchor bolt materials (A36 carbon steel and Type 304 stainless steel) and new candidate alloys (Types 316, 2101, and 2205 stainless steel). Three types of experiments were performed to investigate: (1) corrosion potentials, (2) corrosion macrocell and galvanic coupling effects, and (3) localized corrosion of candidate anchor bolt alloys. Standard metal coupons were cut from 1¼” (3.18cm) diameter anchor bolts with a 3/8” (0.95cm) thickness. Each metal sample used was polished to 600 grit and prepared according to ASTM G1 (6). All electrochemical measurements were made using an SCE reference electrode in a Luggin Capillary filled with saturated KCl solution and a Gamry Potentiostat if required. Dirt samples from around the bearings of the bridges inspected were tested for anion and cation content. From anion and cation results, a standard solution (named normal solution) was chosen for testing, which contained the highest Cl- content and a pH of 7.65. Four different variations were made based on this standard solution: a pH 7.5 solution simulated the exposed environment of the anchor bolt, a pH 13 solution simulated the embedded portion of the bolt; a concentrated solution was also made with both low and high pH and an ion concentration 10 times that of the standard solution to simulate a higher Cl- concentration due to ion precipitation over time. Solution pH was increased by addition of NaOH, and decreased by addition of dilute H2SO4. It was assumed that small additions of these compounds to alter solution pH would not significantly alter the corrosion behavior of the materials tested. The four solution compositions used for testing are given in Table 1. It should be noted that the simulated solution testing performed in this research does not exactly represent the environment present at bridge bearing sites. Simulated solution testing provides little ohmic resistance to corrosion processes, while the environment present at bearing sites is typically one which includes resistivity effects. Simulated solution testing was utilized to provide a fast and conservative answer to the anchor bolt corrosion problem. Therefore, the results presented in this section are only qualitative in nature, allowing for a direct comparison between the various mechanisms present.



TABLE 1 Bearing Site Simulated Solutions Used for Corrosion Testing Ion Concentration (mg/L) Solution

Name Na+ Ca2+ K+ Cl- SO42- NO3

- CO32-

Solution pH

1 - Normal 7.5 59.5 30.5 12.9 40.1 65.3 1.71 56.7 7.5 2 - Normal 13 59.5 30.5 12.9 40.1 65.3 1.71 56.7 13 3 - Concentrated 7.5 595 305 129 401 653 171 567 7.5 4 - Concentrated 13 595 305 129 401 653 171 567 13

Corrosion Potential In order to determine the corrosion behavior of anchor bolt materials in the simulated bearing environment, in-solution corrosion potentials were measured in each solution type. Both galvanized (according to ASTM F1554 specifications for anchor bolts (7)) and non-galvanized A36 carbon steel and Type 304 stainless steel coupons were tested. Non-galvanized A36 carbon steel coupons were only tested in the concentrated solution with a pH of 7.5 (the most aggressive exposure), to determine the protection offered by galvanization. Three different types of exposure were included in each test: (1) ordinary coupons, (2) coupons with crevice washers (following ASTM G78 (8)), and (3) waterline coupons. Type (2) and (3) exposures were used to determine the effects of crevices or atmospheric contact on corrosion behavior. Corrosion potentials were measured using a high-impedance voltmeter against an SCE reference electrode. Electrical contact to the sample was made with the use of a probe consisting of a stainless steel wire encased in glass. A typical in-solution experimental setup for coupon exposure is shown in Figure 5.

FIGURE 5 Typical In-Solution Experimental Setup

Crevice Exposure

Waterline Exposure

Ordinary Exposure



Corrosion Macrocell and Galvanic Coupling Effects For both macrocell and galvanic coupling tests, the linear polarization resistance (LPR) technique was used to determine instantaneous corrosion rates. Coupons to be tested by LPR were coupled electrically and electrolytically (with a solution filled salt bridge) between the experimental setups used for testing corrosion potentials. Prior to coupon coupling, LPR was used to determine an initial “uncoupled” corrosion rate. Once coupons were coupled, corrosion potentials were monitored until steady-state behavior was observed. When steady-state behavior had occurred, LPR was used to determine the “coupled” corrosion rate. This allowed for a quantification of the accelerating effects of macrocell formation at the concrete interface and galvanic coupling of dissimilar metals.

In all cases, an exposed surface area of 10.7 cm2 was used to calculate icorr. A platinum strip with an exposed surface area of approximately 10cm2 was used as the counter electrode. Determination of corrosion rates from LPR data was made using Tafel slopes βa and βc equal to 0.12 for use in the Stearn-Geary equation. Although the 0.12 value differs from those typically used for LPR in reinforced concrete, the environment under study in this research is different from that of an embedded steel reinforcing bar, and the use of a standardized Tafel slope allowed for a direct comparison of corrosion behavior between the various exposures tested. Experimental setups are detailed below. Corrosion Macrocell Simulation of corrosion macrocell formation was performed by coupling coupons between pH 13 (the concrete embedment) and pH 7.5 (the exposed upper portion of the anchor bolt) solutions. Couples of A36 carbon steel and Type 304 stainless steel were made in both normal and concentrated solutions. Galvanic Coupling Type 304 stainless steel and A36 carbon steel coupons were coupled in normal and concentrated pH 7.5 solutions to simulate galvanic effects. It was determined that only pH 7.5 solutions needed to be tested, as galvanic coupling of this type occurs only on the upper portion of the anchor bolt where it meets the bearing’s sole and base plates. Localized Corrosion of Candidate Anchor Bolt Alloys In order to determine the corrosion performance of candidate anchor bolt metallurgies, they were screened using cyclic potentiodynamic polarization scans (9). Potentials were scanned at 2mV/s from -0.5V vs. open circuit potential until the transpassive region was entered. Once in the transpassive region, potential scan rates were reversed. Two types of experimental setups were used for testing samples with and without crevice conditions. An O-ring placed on the surface of the coupon being tested was used to simulate a crevice condition. No-crevice conditions were simulated by masking the coupon’s surface to isolate one area for corrosion. The typical experimental setup is shown in Figure 6. Each specimen had an exposed surface area of 3.7 cm2. All tests were conducted in pH 7.5 normal and concentrated solutions, as these conditions are most critical compared to the strongly passive pH



13 concrete embedment in determining localized corrosion susceptibility. The currently specified Type 304 stainless steel was tested to evaluate its corrosion behavior in the simulated bearing environment. Additionally, three candidate alloys were also tested (Types 316, 2101, and 2205 stainless steel) to determine their behavior with respect to Type 304.

FIGURE 6 Cyclic Potentiodynamic Polarization Experimental Setup RESULTS AND DISCUSSION Corrosion Potential Corrosion potentials were monitored for approximately two months until steady-state results were observed. Results are shown in Figure 7 (a), (b), (c), and (d). “C” denotes A36 carbon steel, and “S” denotes Type 304 stainless steel. In the alkaline pH 13 solutions, both A36 carbon steel and Type 304 stainless steel quickly reached passive potentials of -0.1V to -0.2V vs. SCE and no corrosion occurred. In the pH 7.5 solutions, Type 304 stainless steel maintained a passive potential of -0.1V to -0.2V vs. SCE, while A36 carbon steel samples experienced active corrosion.

KCl Filled Luggin Capillary with SCE Reference Electrode

Connection to Platinum Counter Electrode

One-half of Hydrogen Permeation Chamber Utilized for Testing

Working Electrode with or without O-ring Crevice Former



-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10.0

0 10 20 30 40 50 60 70

Exposure Time (days)

E (

V)

vs. S

CE

(a) Normal pH 7.5

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0 10 20 30 40 50 60 70Exposure Time (days)

E (

V)

vs.

SC

E

(b) Normal pH 13

-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10.0


E (

V)

vs.

SC

E

(c) Concentrated pH 7.5

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0


E (

V)

vs. S

CE

(d) Concentrated pH 13

0 10 20 30 40 50 60 70

Exposur e Time (days)

C - Crevice S - Crevice C - General S - General C - Waterline S - Waterline FIGURE 7 (a), (b), (c), and (d) Corrosion Potential vs. Time

As shown in Figures 7 (a) and (c), A36 carbon steel coupons with zinc galvanization in pH 7.5 solutions began to behave erratically at approximately 30 days. This behavior may indicate the active dissolution of zinc, as A36 carbon steel becomes intermittently cathodically protected. Coupons without the zinc layer (see Figure 7 (c)) remained at an active potential of -0.7V vs. SCE throughout the test with significant corrosion occurring. These results lead to the conclusion that while effective, zinc galvanization may become susceptible to deterioration over the required 75-100+ year design life of new bridges. Thus, all remaining laboratory testing was performed using normal A36 carbon steel coupons. No difference in behavior between ordinary, waterline, and crevice coupons was observed. Differences in corrosion behavior between normal and concentrated solutions were also negligible. Corrosion Macrocell and Galvanic Coupling Effects Coupled and uncoupled corrosion rates determined using LPR are shown in Figure 8. It should be noted that all couples were made with an anode-to-cathode area ratio of 1.0. While this ratio may not necessarily be present in a bearing system, it allows for a standardized comparison between corrosion rates of various types of galvanic and concentration cell couples. It is anticipated that, given the bearing system under examination, anode-to-cathode area ratios should actually be less than 1.0, resulting in further acceleration of corrosion rates, but an

Zn Removed



accurate determination of this is difficult due to the high ohmic resistance present at the site of anchor bolt corrosion. Therefore, corrosion rates presented in Figure 8 are only qualitative in nature, and should only be used for comparative purposes.

0

1

2

3

4

5

6

7

8

9

10

11

A36 to Type 304Galvanic Couple

A36 ConcentrationCell

Type 304Concentration Cell

C

orr

osio

n R

ate

(m

py)

Normal Solution UncoupledNormal Solution CoupledConcentrated Solution UncoupledConcentrated Solution Coupled

FIGURE 8 Concrete Interface Concentration Cell and Galvanic Coupling Results Corrosion Macrocell Results LPR results indicate that accelerated corrosion of A36 carbon steel in a pH 7.5 exposure is possible when an anchor bolt extends between pH 7.5 and pH 13 environments. Type 304 stainless steel corrosion rates remained negligible no matter what type of exposure. A36 carbon steel corrosion rates were accelerated by 4 to 6 times the uncoupled corrosion rate determined using LPR. Little difference was observed between the corrosion behavior in normal and concentrated solution exposures used during the test. Galvanic Coupling Results Corrosion rates of A36 carbon steel coupons when coupled to Type 304 stainless steel coupons with an anode-to-cathode area ratio of 1.0 were found to be accelerated by approximately 10 times the corrosion rate of an individual A36 carbon steel coupon in the simulated bearing environment. Therefore, in the steel girder bridge bearing system, corrosion of A36 carbon steel components (sole plates and girder flanges) may occur when in contact with a Type 304 stainless steel anchor bolt in the presence of a conductive electrolyte. In most cases, galvanic corrosion will be localized at regions of contact, such as between a Type 304 stainless steel washer and an A36 carbon steel sole plate. While galvanic coupling is possible, corrosion rates may be negligible when compared to those found in this research. Investigation of bridges which have utilized Type 304 stainless steel anchor bolts is necessary to determine if galvanic coupling is an actual risk. These bridge inspections have not yet been conducted, but are planned for the future. Similar to the results for concentration cell LPR, little difference was observed between normal and concentrated solution exposures.



Localized Corrosion of Candidate Anchor Bolt Alloys Results of cyclic potentiodynamic polarization scans are shown in Figure 9 below. NS and CS indicate testing performed in normal and concentrated solutions, respectively. The NC subscript indicates tests performed in the no-crevice condition. The shaded rest potential region between -0.1V and -0.2V represents the expected steady-state corrosion potential in the bearing environment for Type 304 stainless steel based on the results shown in Figures 7 (a) and (c) in a pH 7.5 exposure.

-0.75

-0.5

-0.25

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03

log(i) (A/sq.cm)

E (

V)

vs.

SC

E

304 NS 304 CS304 NSNC 304 CSNC316 NS 316 CS2101 NS 2101 CS2205 NS 2205 CS

Rest Potential

FIGURE 9 E vs. log(i) Polarization Scan Results Type 304 Stainless Steel Tests for localized corrosion of Type 304 stainless steel were performed in both the crevice and no-crevice condition. In the crevice condition, Type 304 showed hysteresis, indicating the presence of localized corrosion, which was confirmed by optical microscopy. In the no-crevice condition, localized corrosion did not occur.

Protection potentials when tested in the crevice condition of 0.15V and -0.05V were determined for normal and concentrated exposures, which are 0.1V to 0.3V above the expected steady-state corrosion potential for Type 304 stainless steel in the simulated Georgia bearing environment. Therefore, from the results of crevice and no-crevice condition polarization scans,



Type 304 stainless steel is not expected to be susceptible to localized forms of corrosion if used for anchor bolts in Georgia.

The effect of Cl- content is clearly indicated in Figure 9. In both crevice and no-crevice conditions, potentials were decreased by approximately 0.1V in concentrated solutions. Thus, the effect of Cl- has lowered the potential needed to initiate localized corrosion, a result which is anticipated.

It should be noted that these results are based on the expected environment in Georgia. In cases where more aggresive conditions may be present (industrial environments or areas with high salt concentrations) special consideration should be given to the use of Type 304 stainless steel, and a more corrosion resistant material may be necessary. Type 316, 2101, and 2205 Stainless Steels Tests for localized corrosion of Types 316, 2101, and 2205 candidate stainless steel alloys were performed initially in the crevice condition. No localized corrosion occurred on Type 316, 2101, and 2205 stainless steels when tested in the crevice condition. Because localized corrosion was not initiated in the crevice condition, testing was not performed in the no-crevice condition. These alloys show a strong resistance to localized corrosion in the simulated environment, and therefore should be acceptable for use as anchor bolts in Georgia. Their strong corrosion resistance also lends them to use in more aggressive environments where the use of Type 304 stainless steel may be questionable. CONCLUSIONS AND RECOMMENDATIONS Based on a synthesis of the results of field and laboratory investigations, it can be concluded that the corrosion of steel girder bridge anchor bolts is caused principally by macrocell formation between the portion of the bolt embedded in the concrete and the portion immediately above the concrete in conjunction with the buildup of dirt and debris at the bearing site in pre-1990 bridges. Use of Type 304 stainless steel anchor bolts was found to be an excellent design alternative.

Galvanic coupling and localized corrosion mechanisms were investigated for their effect in post-1990 bridges with Type 304 stainless steel anchor bolts. It was determined that galvanic corrosion of A36 carbon steel when coupled to Type 304 stainless steel may be possible. However, further research, including additional bridge inspections, is necessary to determine if galvanic coupling is a credible risk.

When tested for localized forms of corrosion, Types 304, 316, 2101, and 2205 stainless steel were found to be acceptable for use as anchor bolts in Georgia. However, special consideration should be given when using Type 304 stainless steel in more aggressive environments, as its resistance to localized corrosion is low in comparison to the other alloys tested. ACKNOWLEDGEMENTS This research was sponsored by the Georgia Department of Transportation under Project No. 07-16, Task Order No. 02-42. The findings and conclusions reported herein are those of the authors and do not necessarily represent the opinions, conclusions, specifications, or policies of the Georgia Department of Transportation.



Georgia State Bridge Maintenance Engineers, Mr. Ben Rabun and Mr. Mike Clements, along with Georgia State Bridge and Structures Engineer, Mr. Paul Liles, were very helpful in conducting this research. GDOT engineers Melissa Harper, Lyn Clements, Bill Duvall, Kerry Wood, and Steve St. John all assisted in this study. Their assistance is gratefully acknowledged. REFERENCES 1. Lindquist, L.J., Corrosion of Steel Girder Bridge Anchor Bolts - Masters Thesis. Georgia

Institute of Technology, Atlanta, GA. 2008. 2. Lee, D.J., Bridge Bearings and Expansion Joints. London, UK, E & FN Spon. 1994. 3. Roeder, C.W. and J.F. Stanton, Steel Bridge Bearing Selection and Design Guide, in

Highway Structures Design Handbook. American Iron and Steel Institute & National Steel Bridge Alliance. 1996.

4. FHWA, Status of the Nation's Highways, Bridges, and Transit: Report to Congress. Federal Highway Administration. p. 436. 2006.

5. Liles, P.V., Bridge and Structures Policy Manual. Georgia Department of Transportation. 2007.

6. ASTM, G1 Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens, American Society of Testing and Materials, Editor. 2003.

7. ASTM, F1554 Standard Specification for Anchor Bolts, Steel, 36, 55, and 105-ksi Yield Strength, American Society of Testing and Materials, Editor. 2007.

8. ASTM, G78 Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments, American Society of Testing and Materials, Editor. 2001.

9. ASTM, G61 Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys, American Society of Testing and Materials, Editor. 1998.


CORROSION OF STEEL GIRDER BRIDGE ANCHOR BOLTSdocs.trb.org/prp/09-2517.pdf · Moser, Lindquist...

Documents

Transcript of CORROSION OF STEEL GIRDER BRIDGE ANCHOR BOLTSdocs.trb.org/prp/09-2517.pdf · Moser, Lindquist...