Galvanic Behavior Database for Titanium-Steel Alloy 

Couples 

by Ralph P. I. Adler, Christopher E. Miller, and Brian E. Placzankis 

ARL-TR-2812 September 2002 

Approved for public release; distribution is unlimited. 
NOTICES 

Disclaimers 

The findings in this report are not to be construed as an official Department of the Army position unless 

so designated by other authorized documents. 

Citation of manufacturer’s or trade names does not constitute an official endorsement or approval of the 

use thereof. 

Destroy this report when it is no longer needed. Do not return it to the originator. 
Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5069 

ARL-TR-2812 September 2002 

Galvanic Behavior Database for Titanium-Steel Alloy 

Couples 

Ralph P. I. Adler, Christopher E. Miller, and Brian E. Placzankis 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution is unlimited.
ii

Abstract 

Future lightweight armor for the next generation of lighter material will probably use titanium 

alloy components. These will form galvanic couples with other materials and may induce 

phenomena accelerating the corrosion rate of those metals less noble than titanium. The project 

objective was to evaluate the magnitude of galvanic corrosion between typical ferrous and 

titanium alloys. Electrochemical and accelerated corrosion measurements on both bare and 

Chemical agent resistant coatings (CARC)-coated Ti/steel samples determined accelerated 

corrosion rates. Samples with and without “X-scribed” defects in the CARC coating were 

evaluated. Electrochemical studies on bare Ti/steel couples validated accelerated steel corrosion 

rates but found that intact CARC coatings mitigate corrosion. Even for X-scribed samples, the 

rapid corrosion product buildup in the defect reduced galvanic currents by two orders of 

magnitude. Studies with “Joint A Assembly” CARC-coated samples (phase I: bolted sets of 

Ti/steel plates with intact CARC seals) had virtually no interface corrosion. After examination, 

the rebolted samples with compromised CARC seals had a second accelerated corrosion cycle 

(phase II); the moisture intrusion caused a severe buildup of interface corrosion. Thus Ti/Fe 

interfaces with defect-free CARC coatings can prevent buildup of iron corrosion products. 
iii

Acknowledgments 

The authors want to recognize the following colleagues for their contributions to this report: 

Russell A. Kilbane who was responsible for the setup and experimental measurement of 

potentiodynamic scans and galvanic corrosion cell testing for galvanic corrosion. Dr. Paul F. 

Buckley for his initiation of and technical contributions to this project. Dr. Daniel J. Snoha for 

his expertise in operating the x-ray diffraction equipment and providing quality powder 

diffraction results. Finally, Dr. John H. Beatty for his technical leadership and professional 

advice. 
iv

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v

Contents 

Acknowledgments iii

List of Figures vii

List of Tables ix

1. Introduction 1

2. Experimental Procedure 1

2.1 Experimental Test Plan ...................................................................................................1 

2.1.1 Scientific Assessment of Galvanic Corrosion.......................................................1 

2.1.2 Engineering Assessment of Galvanic Corrosion...................................................1 

2.2 Sample Preparation..........................................................................................................2 

2.2.1 Scientific Test Samples .........................................................................................2 

2.2.2 Engineering Test Samples.....................................................................................2 

2.3 Testing Protocol ..............................................................................................................4 

2.3.1 Testing Protocol for Scientific Samples................................................................4 

2.3.2 Testing Protocol for Engineering Samples............................................................5 

3. Results and Discussion 6

3.1 Scientific Evaluations......................................................................................................6 

3.2 Engineering Evaluations..................................................................................................9 

3.2.1 Salt Fog Exposure Results.....................................................................................9 

3.2.2 Cyclic Corrosion Exposure Results.......................................................................9 

3.2.3 X-ray Characterization of Interface Corrosion Products From Post-Phase II 

(CCT and SFT) “TACOM Joint A Assembly” Samples...............................................10 

4. Conclusions 12

4.1 Scientific Studies...........................................................................................................12 

4.2 Engineering Studies.......................................................................................................15 

5. References 17

Report Documentation Page 19
vi

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vii

List of Figures 

Figure 1. Engineering samples assembled to the “TACOM Joint A Assembly” configuration.....3 

Figure 2. Electrochemical cell assembly for scientific testing. ......................................................4 

Figure 3. ASTM B117 SFT chamber..............................................................................................5

Figure 4. GM9540 P cyclic test chamber........................................................................................6 

Figure 5. Potentiodynamic scans for Ti (upper trace in blue) and Fe (trace in red). ......................7 

Figure 6. Corrosion products on AISI 4130 after 14 days galvanic cell test, (a) no. 4 exposed 

to 0.5N NaCl and (b) no. 2 exposed to 0.005N NaCl. ...............................................................8 

Figure 7. Macrophotos of Ti-steel interfaces after phase I salt fog exposure...............................11 

Figure 8. Macrophotos of Ti-steel interfaces after phase II salt fog exposure. ............................11 

Figure 9. Assembled armor mockup couples after phase II GM 9540P testing exposure............12 

Figure 10. Macrophotos of Ti-steel interfaces after phase I cyclic corrosion exposure...............13 

Figure 11. Macrophotos of Ti-steel interfaces after phase II cyclic corrosion exposure..............13 

Figure 12. Macrophotos of Fe-Fe interfaces after phase II salt fog exposure. .............................14 

Figure 13. Macrophotos of Fe-Fe interfaces after phase II cyclic corrosion exposure.................14 
viii

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ix

List of Tables 

Table 1. Potentiodynamic testing....................................................................................................1 

Table 2. Galvanic corrosion cell testing (Ti 6/4 against 4130).......................................................2 

Table 3. Assessment of galvanic current parameters for Ti/Fe couple...........................................8 

Table 4. X-ray diffraction data for iron oxide phase analysis.........................................................9 

Table 5. Interpretation of corrosion products from galvanic cell Fe substrates..............................9 

Table 6. “Joint A Assembly” interface corrosion rating system...................................................10 

Table 7. “Joint A Assembly” interface corrosion assessment after salt fog exposure..................10 

Table 8. “Joint A Assembly” interface corrosion assessment after cyclic corrosion exposure....12 

Table 9. Interface oxidation products for “Joint A Assembly” samples from x-ray diffraction 

analysis.....................................................................................................................................15 
x

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1

1. Introduction 

Future lightweight armor materials will be required for the next generation of “lighter and more 

lethal and more survivable” materiel. This will involve the use of state-of-the-art, low-cost 

titanium alloy components [1] that will most likely be in electrical contact with structural and 

armor steels as well as other materials. The resulting galvanic couples thus may induce galvanic 

corrosion phenomena and could dramatically accelerate the corrosion rate of the metal that is 

usually less noble than the titanium alloy. The specific objective of this project was to evaluate 

the magnitude of galvanic corrosion effects between typical ferrous and titanium alloys. 

Electrochemical and accelerated corrosion measurements were taken from both bare and 

chemical agent resistant coatings (CARC)-coated Ti/steel samples to determine the galvanically 

accelerated corrosion rates and whether these reach unacceptable rates when a liquid electrolyte 

is present. This gives an indication of the maximum galvanically assisted corrosion rates 

expected because U.S. Army vehicles are often covered with (a film of) water. Comparison 

between bare couples and those with CARC coatings (with and without “defects”) in an aqueous 

environment will indicate the magnitude of the phenomenon and whether further corrosion 

prevention/inhibition remedies are necessary. For CARC-coated Ti/steel couples there must be a 

demonstration that the 15-year corrosion resistance performance is met with a CARC system that 

also meets the Environmental Protection Agency’s compliance goals for FY05. 

2. Experimental Procedure 

2.1 Experimental Test Plan 

2.1.1 Scientific Assessment of Galvanic Corrosion 

See Tables 1 and 2. 

Table 1. Potentiodynamic testing. 

Alloy Concentration of NaCl in Cell Electrolyte 

Ti 6/4 3.5% 

AISI 4130 3.5% 

2.1.2 Engineering Assessment of Galvanic Corrosion 

Accelerated corrosion testing using “Salt Fog Testing” per American Society for Testing of 

Materials (ASTM) Standard B117 [2] and cyclic corrosion testing per the GM 9540P 
2

Table 2. Galvanic corrosion cell testing (Ti 6/4 against 4130). 

Condition Concentration of NaCl in Cell Electrolyte 

Bare couple 0.005N 

Bare couple 0.5N 

CARC coating (w/o defects) 0.005N 

CARC coating (w/o defects) 0.5N 

CARC coating (w/scratch defect) 0.005N 

CARC coating (w/scratch defect) 0.5N 

protocol [3] was performed on CARC-coated “TACOM* Joint A Assembly” samples [4]. 

Specific combinations (Ti/Ti; Ti/Fe; and Fe/Fe) of Ti 6/4 and 4130 plates were through-hole 

bolted together with a grade 8 fastener followed by thorough CARC coating. Both phase I 

accelerated corrosion testing protocols involved testing each assembly with an intact interface 

sealed by the CARC coating. After phase I, each couple was disassembled and the internal 

common plate interface examined. The re-assembled sample with its broken CARC-interface 

seal, which then allows fluid entrainment, was then resubjected to a second series (phase II) with 

an identical sequence of phase I accelerated testing exposures. 

2.2 Sample Preparation 

2.2.1 Scientific Test Samples 

Samples for electrochemical and engineering testing were produced from existing supplies of 

Titanium 6/4 (6 w/o aluminum; 4 w/o vanadium) alloy and American Iron and Steel Institute 

(AISI) 4130 steel. All scientific test samples had two parallel faces, but size and shape varied. 

Prior to potentiodynamic or galvanic corrosion cell testing, the “bare” specimens were abraded 

with 600-grit silicon carbide paper, rinsed in distilled water, degreased in acetone, rinsed again in 

distilled water, and then dried. One square centimeter of each bare specimen was exposed to the 

test solution. The “coated” samples had the machined surfaces pretreated with DOD-P-15328 

[5], then primed with MIL-P-53022 [6], and topcoated with MIL-C-53039 [7]. One square 

centimeter of each “coated” specimen with or without an “X-scribed” defect was exposed to the 

test solution. 

2.2.2 Engineering Test Samples 

Engineering samples were assembled to the “TACOM Joint A Assembly” configuration that is 

described schematically in Figure 1. 2 × 2 × 1-in plates of Ti and steel were individually gritblasted to a near-white finish. Then specific combinations (Ti/Ti; Ti/Fe; and Fe/Fe) of these 

plates were “through-hole bolted together” with a grade 8 fastener torqued to 180 ft-lb. Each 

assembly, including the bolt/nut and washer, was then pretreated with DOD-P-15328 [5], then 

liberally primed with MIL-P-53022 [6], and then topcoated with MIL-C-53039 [7] that formed 

an effective seal against fluid intrusion. 

 *

 TACOM = U.S. Army Tank-automotive and Armaments Command. 
3

Figure 1. Engineering samples assembled to the “TACOM Joint A Assembly” configuration. 
4

2.3 Testing Protocol 

2.3.1 Testing Protocol for Scientific Samples 

More specific details and a description of the equipment used can be found in Miller et al. [8]. 

Figure 2 depicts the electrochemical cell assembly that was used for both series of scientific 

tests. 

Specimen Locations 

Figure 2. Electrochemical cell assembly for scientific testing. 

Potentiodynamic tests were conducted at room temperature in an aerated cell containing about 

400 mL of the test solution. The model K0235 cells were manufactured by Princeton Applied 

Research (PAR), with a platinum-plated electrode at one end of the cell and a sample holder at 

the other end. A computer-controlled Schlumberger SI 1280 electrochemical measurement unit 

was used. The open-circuit potentials were measured against a saturated calomel electrode 

(SCE) for one hour before the scans commenced. A scan rate of 0.1667 mV/s was used. 

Potentiodynamic scans were performed in standard 3.5% NaCl aqueous solutions. 

Galvanic tests were performed in two concentrations of salt solutions (0.5N and 0.005N NaCl), 

but could not be performed in distilled water due to its high resistivity. For high humidity 

atmospheric exposures, the 0.5N NaCl solution may be too severe but was still run for 

comparative reasons. A modified version of the PAR K0235 with sample holders at both ends 

for coupling the Ti 6/4 and 4130 specimens was used for the galvanic corrosion tests (Figure 2). 

In this test setup, a Keithley* Multiplexer with single-pole double-throw switches was used to 

 *

 Keithley is a trademark of Test Instrumentation Group, 28775 Aurora Road, Cleveland, OH 44139. 
5

sequentially multiplex between each of the six (nitrogen) aerated cells and a PAR 273 

Potentiostat/Galvanostat. A potential difference between samples of 0 V was maintained (an 

effective short circuit) while simultaneously measuring the galvanic current (I) that is 

proportional to the corrosion rate. The galvanic currents were measured over a minimum of two 

weeks (for the bare and defect-free coated samples) or four weeks for the coated samples with Xscribed defects (to reach an apparent steady state current value). 

2.3.2 Testing Protocol for Engineering Samples 

2.3.2.1 Salt Fog Testing (SFT). SFT of “TACOM Joint A Assembly” samples were performed 

according to ASTM B117 [2] protocol in two phases. Figure 3 shows the SFT chamber and lists 

the exposure parameters. The phase I exposure of 2500 hr was performed with an unbroken 

CARC seal. After unbolting and breaking the CARC seal, the interface was examined for any 

corrosion phenomena. Subsequently each couple, after one plate was rotated by 90° and rebolted 

to snug fit state, was given a second 2500-hr exposure (phase II) without the benefit of the 

original CARC seal. Sample interface characterization was then again documented. 

Figure 3. ASTM B117 SFT chamber. 

2.3.2.2 Cyclic Corrosion Testing (CCT). CCT of another series of “TACOM Joint A 

Assembly” samples were performed according to General Motors (GM) 9540P [3] protocol in 

two phases. Figure 4 shows the cyclic test chamber and lists the exposure parameters. The phase 

I exposure of 100 cycles was performed with an unbroken CARC seal. After unbolting and 

breaking the CARC seal, the interface was examined for any corrosion phenomena. 
6

Figure 4. GM9540 P cyclic test chamber. 

Subsequently each couple, after one plate was rotated by 90° and rebolted to snug fit state, was 

given a second 100-cycle exposure (phase II) without the benefit of the original CARC seal. 

Sample interface characterization was then again documented. 

3. Results and Discussion 

3.1 Scientific Evaluations 

The potentiodynamic scans for the Ti and steel samples in 3.5% NaCl aqueous solution are 

shown in Figure 5. The various electrochemical parameters were estimated as follows: (1) 

corrosion potential for Ti 6/4 = !0.35 V, (2) corrosion potential for AISI 4130 = !0.8V, and (3) 

mixed corrosion potential (for Ti 6/4 with AISI 4130) = !0.75 V. Note that the mixed corrosion 

current was an order of magnitude greater than that for the corrosion current for AISI 4130. 

Galvanic current is a useful indicator of the behavior of two different materials that are in 

electrical contact with each other in a specific environment. Larger currents indicate that 

galvanically assisted corrosion is occurring that is proportional to the effective contact area and 

the galvanic potential difference between the materials in the coupled sample. Smaller currents 
7

Figure 5. Potentiodynamic scans for Ti (upper trace in blue) and Fe (trace in red). 

indicate that either there is a small galvanic differential between the materials or that the kinetics 

of the corrosion reaction are quite slow. If the current decreases with exposure time, it may be 

that the buildup of corrosion products acts as a partial barrier. In the present case, the galvanic 

current (I) provides an assessment of the relative corrosion rates as a function of electrolytic salt 

concentration for bare and CARC-coated samples as well as CARC-coated samples with 

deliberately X-scribed defects. The results and observations are listed in Table 3. 

Characterization of the corrosion products on the bare iron substrates is depicted in Figure 6 for 

samples exposed to 0.005N and 0.5N NaCl solutions (sample nos. 4 and 2, respectively) and has 

also been included in the next series of tables. 

X-ray results were obtained using a “2 theta” flat sample diffractometer with Cu K-alpha 

radiation [9]. By measuring and then ratioing the intensities of the strongest diffraction peaks 

from the iron substrate and the two iron oxide phases (i.e., magnetite [Fe3O4] and hematite 

[Fe2O3]), information about the corrosion products formed on the 4130 steel substrate during the 

“bare”galvanic current tests can be obtained. The relevant x-ray diffraction data is listed in 

Table 4. Analysis of this x-ray diffraction data has been interpreted to show that the 

concentration of NaCl in the electrolyte produces differences in total oxide thickness and the 

relative volume fraction of the hematite and magnetite phases and is presented in Table 5. 
8

Table 3. Assessment of galvanic current parameters for Ti/Fe couple. 

 (a) (b) 

Figure 6. Corrosion products on AISI 4130 after 14 days galvanic cell test, 

(a) no. 4 exposed to 0.5N NaCl and (b) no. 2 exposed to 0.005N 

NaCl. 

The resultant observations are that (1) the total oxide layer thickness for the sample exposed to 

the 0.5N NaCl solution was about twice that for the sample exposed to the 0.005N NaCl 

solution; (2) the sample exposed to the 0.5N NaCl solution had an outer layer of Fe2O3 

(hematite) with a layer Fe3O4 (magnetite) adjacent to the steel with some residual NaCl in these 

oxides; (3) the sample exposed to the dilute 0.005N NaCl solution had thinner layers of both 

Fe3O4 and Fe2O3 compared to the thicker ones from the more concentrated 0.5N NaCl exposed 

sample; and (4) the relative volume fraction of the Fe2O3 phase in the total oxide coating was 

larger for the 0.5N NaCl exposed sample compared to that for the sample exposed to a lower 

concentration of NaCl. 
9

Table 4. X-ray diffraction data for iron oxide phase analysis. 

Table 5. Interpretation of corrosion products from galvanic cell Fe substrates. 

3.2 Engineering Evaluations 

After exposure of “TACOM Joint A Assembly” samples to either SFT or CCT (for both phase I 

or II), the common interface was examined for corrosion products. An arbitrary, qualitative 

ranking methodology was devised to assign a metric for the extent of corrosion product formed 

at this interface and has been listed in Table 6. Observations of these common interfaces were 

qualitatively described and given a rating (where “zero” means no corrosion was observed, and 

“10” means the most extensive corrosion product buildup was observed) after either phase I or II 

exposures. 

3.2.1 Salt Fog Exposure Results 

Table 7 provides the interface corrosion assessment after salt fog exposure. Illustrative 

macrophotos of these interfaces after salt fog exposures are provided for the Ti-steel interfaces 

for phase I (Figure 7) and phase II (Figure 8). 

3.2.2 Cyclic Corrosion Exposure Results 

Figure 9 depicts the external macrostructure of all “TACOM Joint A Assembly” samples after 

phase II GM 9540P [3] accelerated testing exposure. Table 8 provides the interface corrosion 

assessment of these samples after phase I and II cyclic corrosion exposures. Illustrative 
10

Table 6. “Joint A Assembly” interface corrosion rating system. 

Rating Qualitative Description Reference 

0(zero) No Interface Corrosion SF & GM phase I for Ti/Ti 

1 No Significant Corrosion SF phase I for Ti/Fe & Fe/Fe 

2 Slight Corrosion (greater than for SF Ph I=#1) GM phase I for Ti/Fe 

3 Some Corrosion (greater than GM Ph I for Ti/Fe=#2) GM phase I for Fe/Fe 

 

4 

5 More Corrosion (greater than GM Ph I for Fe/Fe=#3) SF phase II for Ti/Fe 

 

6 

7 Severe Corrosion (greater than SF Ph II for Ti/Fe=#5) SF phase II for Fe/Fe 

 

8 

9 Very Severe Corrosion; Rust Exfoliation (less than for Fe/Fe=#10) GM phase II for Ti/Fe 

10 Most Severe Corrosion; Major Rust Exfoliation GM Phase II for Fe/Fe 

Table 7. “Joint A Assembly” interface corrosion assessment after salt fog exposure. 

macrophotos of these interfaces after salt fog exposures are provided for the Ti-steel interfaces 

after phase I (Figure 10) and phase II (Figure 11). To be noted is that the buildup of interfacial 

corrosion products is even greater in the comparable Fe-Fe samples as listed in Tables 7 and 8 

and illustrated in Figure 12 for salt fog and Figure 13 for cyclic corrosion phase II exposures. 

Clearly, the CCT protocol provides a more aggressive accelerated testing environment due to the 

programmed cyclic changes in thermal and chemical conditions compared to the constant 

exposure conditions within the SFT-accelerated testing chamber. 

3.2.3 X-ray Characterization of Interface Corrosion Products From Post-Phase II (CCT 

and SFT) “TACOM Joint A Assembly” Samples 

After phase II exposures, scrapings/flakes of the interfacial corrosion product were examined 

using the same x-ray diffraction techniques as were used for the previous scientific samples. The 

intent was to qualitatively determine if differences in the relative volume fractions of hematite 

and magnetite in the oxide occurred due to the two different accelerated testing methodologies. 
11

Figure 7. Macrophotos of Ti-steel interfaces after phase I salt fog exposure. 

Figure 8. Macrophotos of Ti-steel interfaces after phase II salt fog exposure. 
12

Figure 9. Assembled armor mockup couples after phase II GM 9540P testing exposure. 

Table 8. “Joint A Assembly” interface corrosion assessment after cyclic corrosion exposure. 

The results listed in Table 9 indicate that at Fe/Fe interfaces the salt fog exposures produced a 

primarily hematite oxide phase while the cyclic corrosion produced a primarily magnetite 

product. For samples with Ti/Fe interfaces, the volume fraction of the minority oxide seems to 

be increased for either testing protocol. 

4. Conclusions 

4.1 Scientific Studies 

An initial Ti (6/4)-Fe (AISI 4130) galvanic corrosion database for an aqueous environment was 

established. Potentiodynamic scans using a conventionally accepted open cell with a 3.5% NaCl 

aqueous solution validated that a more noble Ti cathode increased the mixed couple galvanic 

current by an order of magnitude, thus increasing the corrosion rate at the (4130) steel anode. 
13

Figure 10. Macrophotos of Ti-steel interfaces after phase I cyclic corrosion exposure. 

Figure 11. Macrophotos of Ti-steel interfaces after phase II cyclic corrosion exposure. 
14

Figure 12. Macrophotos of Fe-Fe interfaces after phase II salt fog exposure. 

Figure 13. Macrophotos of Fe-Fe interfaces after phase II cyclic corrosion exposure. 
15

Table 9. Interface oxidation products for “Joint A Assembly” samples from x-ray diffraction analysis. 

During galvanic cell testing of the bare Ti/Fe couples, the buildup of an oxide layer on the Fe 

anode was faster and thicker in the 0.5N NaCl than in the 0.005N NaCl electrolyte cell. The 

presence of this oxide layer effectively increased the electrical resistance of this circuit for either 

concentration electrolyte cell nominally reducing the steady state galvanic current to half of the 

initial maximum current observed. In both cases, magnetite was the major oxide phase formed 

but the minority volume fraction was higher for the hematite phase formed in the 0.5N NaCl cell; 

this shift may be a result of the differences in the kinetics of oxide formation. 

No galvanic current was measured during galvanic cell testing of the CARC coated Ti/Fe 

couples for either NaCl concentration cell; thus the CARC layer was very protective in isolating 

both the anode and cathode from the electrolyte. For both NaCl concentration cells, even 

deliberate X-scribed defects in the CARC experienced rapid buildup of a corrosion product in the 

defect. Thus, compared to the bare couples, the measured galvanic current was reduced by two 

orders of magnitude for the 0.005N NaCl cell and three orders of magnitude for the 0.5N NaCl 

cell, respectively. This means that as a practical matter, small defects in CARC should 

experience a rapid buildup of an oxide product that could partially block subsequent electrolyte 

access to the rest of the steel substrate. 

4.2 Engineering Studies 

Accelerated “TACOM Joint A Assembly” SFT of phase I samples that had unbroken CARC 

seals between the Ti/Fe plates had virtually no corrosion along the contacting iron interface 

because there was no fluid intrusion. Similar accelerated “TACOM Joint A Assembly” cyclic 

corrosion testing of phase I samples had minor corrosion along the contacting iron interface due 

to localized compromises in the CARC seal between the Ti/Fe plates. Thus, in most cases, the 

presence of a quality CARC coating can help exclude electrolytes between contacting dissimilar 

metal plates, thus mitigating galvanically induced corrosion product buildup. 

During phase II accelerated “TACOM Joint A Assembly” salt fog and cyclic corrosion testing, 

the absence of the CARC seal allowed the intrusion of moisture/electrolyte into the crevasse 

between the two bolted plates leading to corrosion at the contacting iron interface. Thus, there 

was a significant buildup of Fe corrosion products in the crevasse between both Fe/Fe and Ti/Fe 

interfaces during salt fog exposures. For Fe/Fe couples, hematite was the primary oxide phase 

with a minor amount of magnetite; for Ti/Fe couples, the presence of Ti apparently produced a 
16

nearly even mix of both magnetite and hematite but the total quantity of corrosion product was 

less than for the Fe/Fe couples. 

For cyclic corrosion phase II exposures there was severe oxidation/exfoliation of corrosion 

products again due to the presence of moisture/electrolyte in the crevasse between either the 

Fe/Fe or Ti/Fe interfaces. For Fe/Fe couples, magnetite was the primary oxide phase with a 

minor amount of hematite; for Ti/Fe couples the presence of Ti 6/4 apparently caused the 

formation of an oxide mixture of mainly magnetite with some hematite, but the quantity of 

corrosion product was again less than for the Fe/Fe couples. 

To be noted is that phase II CCT Fe/Fe samples produced the greatest amount of interfacial 

corrosion products for all samples examined in this study. Thus, clearly for an engineering 

corrosion propensity screening tool, the CCT protocol—due to the programmed cyclic changes 

in thermal and chemical conditions compared to the constant exposure conditions within the 

SFT-accelerated testing chamber—provides a more rigorous and aggressive accelerated testing 

methodology. 

Thus, mixed Ti/Fe interfaces that are protected/sealed from the environment by CARC coatings 

will not experience unacceptable galvanically accelerated corrosion phenomena. Accordingly, 

mixing titanium and steel components on U.S. Army materiel, provided they are protected by a 

quality CARC coating, will not cause adverse durability problems or lead to increased 

maintenance issues and costs.
17

5. References 

1. Montgomery, J. S., M. G. H. Wells, B. Roopchand, and J. S. Ogilvy. “Low-Cost Titanium 

Armors for Combat Vehicles.” Journal of Metals, vol. 49, no. 5, pp. 45–47, May 1997. 

2. American Society for Testing and Materials. “Standard Method of Salt Spray (Fog) 

Testing.” ASTM B117, West Conshohocken, PA, 1990. 

3. General Motors. “Accelerated Corrosion Test GM 9540P.” General Motors Engineering 

Standard GM 9540P, 1997. 

4. Levy, M., B. E. Placzankis, R. Brown, R. Huie, M. Kane, and G. McAllister. “The Effects 

of Co-Mingling Dissimilar Fastener Coatings on the Corrosion Behavior of Steel Bolt 

Assemblies.” MTL TR 92-40, U.S. Army Materials Technology Laboratory, Watertown, 

MA, July 1992. 

5. U.S. Department of Defense. “Primer (Wash) Pretreatment (Formula No. 117 for Metals).” 

DOD-P-15328, revision D, amendment 2, Washington, DC, March 1991. 

6. U.S. Department of Defense. “Primer, Epoxy Coating, Corrosion Inhibiting, Lead and 

Chromate Free.” MIL-P-53022-10, Washington, DC, February 1992. 

7. U.S. Department of Defense. “Coating. Aliphatic Polyurethane, Single Component, 

Chemical Agent Resistant.” MIL-C-53039A, Washington, DC, May 1993. 

8. Miller, C. E., J. H. Beatty, J. V. Kelley, B. E. Placzankis, and P. F. Buckley. “Galvanic and 

Potentiodynamic Corrosion Studies of Depleted Uranium and Sabot Materials.” ARL-TR2047, U.S. Army Research Laboratory, Aberdeen Proving Ground, MD, September 1999. 

9. Cullity, B. D. Elements of X-ray Diffraction. Second Edition, Reading, MA: AddisonWesley, chapters 6, 7, and 10. 
18

INTENTIONALLY LEFT BLANK. 

.
19

 corrosion, titanium, steel, CARC coating 25

Future lightweight armor for the next generation of lighter material will probably use titanium alloy components. These

will form galvanic couples with other materials and may induce phenomena accelerating the corrosion rate of those

metals less noble than titanium. The project objective was to evaluate the magnitude of galvanic corrosion between

typical ferrous and titanium alloys. Electrochemical and accelerated corrosion measurements on both bare and Chemical

agent resistant coatings (CARC)-coated Ti/steel samples determined accelerated corrosion rates. Samples with and

without "X-scribed" defects in the CARC coating were evaluated. Electrochemical studies on bare Ti/steel couples

validated accelerated steel corrosion rates but found that intact CARC coatings mitigate corrosion. Even for X-scribed

samples, the rapid corrosion product buildup in the defect reduced galvanic currents by two orders of magnitude. 

Studies with "Joint A Assembly" CARC-coated samples (phase I: bolted sets of Ti/steel plates with intact CARC seals)

had virtually no interface corrosion. After examination, the rebolted samples with compromised CARC seals had a

second accelerated corrosion cycle (phase II); the moisture intrusion caused a severe buildup of interface corrosion. 

Thus Ti/Fe interfaces with defect-free CARC coatings can prevent buildup of iron corrosion products. 

ARL-TR-2812

U.S. Army Research Laboratory

ATTN: AMSRL-WM-MC

Aberdeen Proving Ground, MD 21005-5069

Ralph P. I. Adler, Christopher E. Miller, and Brian E. Placzankis

Galvanic Behavior Database for Titanium-Steel Alloy Couples VEPRO 3H

September 2002 Final, January 2000–December 2001

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Standard Form 298 (Rev. 2-89)

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INTENTIONALLY LEFT BLANK. 
NO. OF NO. OF 

COPIES ORGANIZATION COPIES ORGANIZATION

1

 2 DEFENSE TECHNICAL 

 INFORMATION CENTER 

 DTIC OCA 

 8725 JOHN J KINGMAN RD 

 STE 0944 

 FT BELVOIR VA 22060-6218 

 1 COMMANDING GENERAL 

 US ARMY MATERIEL CMD 

 AMCRDA TF 

 5001 EISENHOWER AVE 

 ALEXANDRIA VA 22333-0001 

 1 INST FOR ADVNCD TCHNLGY 

 THE UNIV OF TEXAS AT AUSTIN 

 3925 W BRAKER LN STE 400 

 AUSTIN TX 78759-5316 

 1 US MILITARY ACADEMY 

 MATH SCI CTR EXCELLENCE 

 MADN MATH 

 THAYER HALL 

 WEST POINT NY 10996-1786 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRL D 

 DR D SMITH 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRL CI AI R 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 3 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRL CI LL 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 3 DIRECTOR 

 US ARMY RESEARCH LAB 

 AMSRL CI IS T 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

ABERDEEN PROVING GROUND

 2 DIR USARL 

 AMSRL CI LP (BLDG 305) 
NO. OF NO OF 

COPIES ORGANIZATION COPIES ORGANIZATION

2

 2 PROJECT MANAGER 

 MEDIUM TACTICAL VEHICLES 

 SFA GCSS W MTV 

 WARREN MI 48397-5000 

 2 US ARMY TACOM ARDEC 

 AMSTA AR WET 

 J ARGENTO 

 BLDG 172 IEC 

 PICATINNY ARSENAL NJ 

 07806 

 1 NSWC 

 MARINE CORROSION BR 

 B BIEBERICH 

 9500 MACARTHUR BLVD 

 BLDG 60 CODE 613 

 WEST BETHESDA MD 

 20817-5700 

 3 US ARMY AMCOM 

 AMSM RD PS AM 

 S F CARR 

 J R CURTIS 

 A P STEEL 

 REDSTONE ARSENAL AL 

 35898 

 1 NSWC 

CARDEROCK DIV 

 CODE 624 

 5001 S BROAD ST CARDEROCK 

 PHILADELPHIA PA 19112-5083 

 10 US ARMY TACOM ARDEC 

 AMSTA TR E 

 J H KOVANDA 

 6501 ELEVEN MILE RD 

 WARREN MI 48397-5000 

 3 CONCURRENT TECHNOLOGIES 

 CORP 

 L GINTERT 

 B MANTY 

 M SINGLETON 

 7990 114TH AVENUE 

 LARGO FL 33773 

 3 US ARMY TACOM ARDEC 

 BENET LABORTORIES 

 AMSTA AR CCB T 

 R DILLON 

 J VASILAKIS 

 G KENDALL 

 BLDG 115 

 WATERVLIET NY 12189-4050 

 2 US ARMY TARDEC 

 AMSTA TR E MEPS 267 

 C HANDSY 

 T M LANDY 

 6501 ELEVEN MILE RD 

 WARREN M 48397--5000 

 4 PM BRADLEY ENVR MGMT TEAM 

 GM HOERAUF (2 CPS) 

 E MILLER (2 CPS) 

 1650 RESEARCH DR 

 SUITE 115 

 STERLING HEIGHTS MI 48083 

 1 TACOM ARDEC RIA 

 AMSTA AR ESM H 

 J MENKE 

 ROCK ISLAND ARSENAL 

 ROCK ISLAND IL 61299 

 2 CORRPRO COMPANIES INC 

 J REPP 

 P AULT 

 50 TENNESSEE AVENUE 

 OCEAN CITY NJ 08226 

 1 US ARMY TACOM 

 AMSTA TR E MERS 

 G SHAW 

 WARREN MI 48092 

 1 AM GENERAL CORP 

 D F BOULTON 

 31744 ENTERPRISE DR 

 LIVONIA MI 48151-3330 
NO. OF NO OF 

COPIES ORGANIZATION COPIES ORGANIZATION

3

 1 US ARMY ARDEC 

 AMSTA AR WEA 

 J F SENSKE 

 BLDG 355 

 PICATINNY ARSENAL NJ 

 07806-5000 

 1 CTC UNITED DEFENSE 

 J DORSCH 

 1205 COLEMAN AVE 

 SANTA CLARA CA 95050 

 1 US AIR FORCE RSCH LAB 

 T NAGUY 

 SUITE 1 

 2179 TWELFTH STREET 

 WPAFB OH 45433-7718 

 2 US ARMY SBCCOM 

 NATICK SOLDIER CENTER 

 SCIENCE & TECHNOLOGY DIR 

 M BRAY 

 F ALLEN 

 KANSAS ST 

 NATICK MA 01760-5018 

 2 NAVAIR 

 CODE 4341 UNIT 5 

 M J KANE 

 C MATZDORF 

 48066 SHAW ROAD 

 BLDG 2188 

 PATUXENT RIVER MD 

 20670 

 1 RED RIVER ARMY DEPOT 

 AMSTA RR ME 

 M A STARKS 

 100 MAIN DR 

 TEXARKANA TX 75507-5000 

 1 US ARMY IEC 

 AMSTA AR WET 

 J P THEIS 

 BLDG 172 

 PICATINNY ARSENAL NJ 

 07806 

 4 AIR FORCE RSCH LAB 

 AFRL MLBT 

 M S DONLEY (MLBT) 

 R A MANTZ (MLBT) 

 D T PEELER (MLO) 

 L M PFLEDDERER (MLSA) 

 WPAFB OH 45424 

ABERDEEN PROVING GROUND

 1 US ARMY ATC ARL 

 AMSRL WM MO 

 W ZIEGLER 

 BLDG 4600 

 APG MD 21005-5069 

 1 US ARMY EVALUATION CTR 

 CSTE AEC CSE CS 

 4120 SUSQUEHANNA AVE 

 APG MD 21005-3013 

 2 US ARMY ATC 

 B MULLIS 

 BLDG 358 

 APG MD 21005-5059 

 2 US ARMY ENVIRONMENTAL 

 CENTER 

 R L EICHOLTZ 

 A J WALKER 

 5179 HOADLEY RD 

 APG MD 21010-5401 

 44 DIR USARL 

 AMSRL WM MA 

 J ESCARSEGA (2 CPS) 

 W LUM 

 R HINXMAN 

 J L DUNCAN 

 K G CHESONIS 

 W E KOSIK 

 S H MCKNIGHT
NO. OF 

COPIES ORGANIZATION

4

 AMSRL WM MC 

 R ADLER (20 CPS) 

 B E PLACZANKIS (2 CPS) 

 C MILLER (2 CPS) 

 J BEATTY (3 CPS) 

 J D DEMAREE 

 J MONTGOMERY 

 J V KELLEY 

 J K HIRVONEN 

 R J SQUILLACIOTI 

 AMSRL WM MD 

 V K CHAMPAGNE 

 S M GRENDAHL 

 D J SNOHA (2 CPS) 
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