Corrosion Immersion Testing of 13-mm-Diameter 

Grade-10.9 Bolts for Bolt-on Armor 

by Tom Considine and Tom Braswell 

ARL-CR-654 July 2010 

prepared by 

Oak Ridge Institute for Science and Education 

4692 Millennium Dr., Ste. 101 

Belcamp, MD 21017 

and 

Versar 

6850 Versar Center 

Springfield, VA 22151 

under contract 

W91236-04-D-0083/D00114 

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-CR-654 July 2010 

Corrosion Immersion Testing of 13-mm-Diameter 

Grade-10.9 Bolts for Bolt-on Armor 

Tom Considine 

Oak Ridge Institute for Science and Education 

Tom Braswell 

Versar

prepared by 

Oak Ridge Institute for Science and Education 

4692 Millennium Dr., Ste. 101 

Belcamp, MD 21017 

and 

Versar 

6850 Versar Center 

Springfield, VA 22151 

under contract 

W91236-04-D-0083/D00114 

Approved for public release; distribution is unlimited. 
ii

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering 

and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, 

including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson 

Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to 

comply with a collection of information if it does not display a currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

July 2010 

2. REPORT TYPE 

Final 

3. DATES COVERED (From - To) 

1 October 2008–1 July 2009 

4. TITLE AND SUBTITLE 

Corrosion Immersion Testing of 13-mm-Diameter Grade-10.9 Bolts for Bolt-on 

Armor 

5a. CONTRACT NUMBER 

W91236-04-D-0083/D00114 

5b. GRANT NUMBER 

5c. PROGRAM ELEMENT NUMBER 

6. AUTHOR(S) 

Tom Considine and Tom Braswell†

5d. PROJECT NUMBER 

02121208A 

5e. TASK NUMBER 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION 

 REPORT NUMBER 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 

U.S. Army Research Laboratory 

ATTN: RDRL-WMM-C 

Aberdeen Proving Ground, MD 21005-5069 

10. SPONSOR/MONITOR’S ACRONYM(S) 

11. SPONSOR/MONITOR'S REPORT 

 NUMBER(S) 

ARL-CR-654 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

Approved for public release; distribution is unlimited. 

13. SUPPLEMENTARY NOTES 



Oak Ridge Institute for Science and Education, 4692 Millennium Dr., Ste. 101, Belcamp, MD 21017 

†

Versar, 6850 Versar Center, Springfield, VA 22151

14. ABSTRACT 

This experiment examined the performance of selected coatings and pretreatments on 13-mm grade-10.9 bolts immersed in a 

5% NaCl solution in an attempt to evaluate the corrosion prevention properties of each selected coating and pretreatment 

relevant to those selected for bolt-on armor. Five candidate finishes as well as zinc plating in accordance with ASTM B 633 

with hexavalent chromium conversion coating as control were tested. Each bath was heated to 75 °F, and the salt solution was 

agitated in order to prevent stagnation and ensure equal heating. Testing was completed over 500 h, with visual inspections and 

open circuit potential measurements at 1, 2, 4, 8, and 24 h, and once every 24 h following. In this experiment, corrosion creep 

was defined visually as frosting for the onset of corrosion and red rust in the percentage of the fastener affected, each yielding 

separate observations. 

15. SUBJECT TERMS

bolt, armor, chromium, hexavalent, TCP, AlumiPlate, MagniPlate, immersion 

16. SECURITY CLASSIFICATION OF: 

17. LIMITATION 

OF ABSTRACT 

UU 

18. NUMBER 

OF PAGES 

22 

19a. NAME OF RESPONSIBLE PERSON

Thomas Considine 

a. REPORT 

Unclassified

b. ABSTRACT 

Unclassified

c. THIS PAGE 

Unclassified

19b. TELEPHONE NUMBER (Include area code) 

410-306-0951 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
iii

Contents 

List of Figures iv

Acknowledgments v

1. Introduction 1

2. Methods and Materials 1

3. Test Candidates 1

4. Experimental Procedure 2

5. Results and Discussion 3

6. Conclusions 15

Distribution List 16 
iv

List of Figures 

Figure 1. Bolt/screw assembly. .......................................................................................................2

Figure 2. (a) Prepared bolts prior to immersion and (b) immersion bath setup. .............................3

Figure 3. Visual corrosion on immersed bolts. ...............................................................................4

Figure 4. Open circuit potential of immersed bolts. .......................................................................4

Figure 5. Bare bolts immediately after immersion. ........................................................................5

Figure 6. Hexavalent chrome/zinc bolts immediately after immersion. .......................................5

Figure 7. TCP/zinc bolts immediately after immersion. .................................................................5

Figure 8. AlumiPlate bolts immediately after immersion. ..............................................................6

Figure 9. MagniPlate 565 immediately after immersion. ...............................................................6

Figure 10. MagniPlate 594 immediately after immersion. .............................................................6

Figure 11. Bare steel, hexavalent chrome/zinc, and TCP/zinc after drying. ..................................7

Figure 12. AlumiPlate, MagniPlate 565, and MagniPlate 594 after drying. ..................................8

Figure 13. Visual corrosion on immersed bolts in supplementary experiment. .............................9

Figure 14. Open circuit potential of immersed bolts in supplementary experiment. ....................10

Figure 15. Bare bolts immediately after immersion in supplementary experiment. .....................10

Figure 16. Hexavalent chrome/zinc bolts immediately after immersion in supplementary 

experiment................................................................................................................................11

Figure 17. TCP/zinc bolts immediately after immersion in supplementary experiment. .............11

Figure 18. AlumiPlate bolts immediately after immersion in supplementary experiment. ..........11

Figure 19. MagniPlate 565 immediately after immersion in supplementary experiment. ............12

Figure 20. MagniPlate 594 immediately after immersion in supplementary experiment. ............12

Figure 21. Bare steel, hexavalent chrome/zinc, and TCP/zinc after drying in supplementary 

experiment................................................................................................................................13

Figure 22. AlumiPlate, MagniPlate 565, and MagniPlate 594 after drying in supplementary 

experiment................................................................................................................................14
v

Acknowledgments 

This research was supported in part by an appointment to the Student Research Participation 

Program at the U.S. Army Research Laboratory (ARL) administered by the Oak Ridge Institute 

for Science and Education through an interagency agreement between the U.S. Department of 

Energy and ARL. 
vi

INTENTIONALLY LEFT BLANK. 
1

1. Introduction 

Finding a replacement for hexavalent chromium-based finishes for fasteners was the driver for 

this experiment. The purpose of this experiment was to quantify the corrosion-inhibiting 

performance of the selected coatings for the 13-mm bolts and to determine the possible preferred 

selection for the customer. Immersion corrosion testing was chosen for this experiment because 

of its acceleration of corrosion to quickly showcase weaknesses, and it is the second phase of 

testing done with respect to the candidates for bolt-on armor. Experimental procedures for this 

evaluation were basic and did not include the wear and tear that fasteners typically would receive 

during processing storage, assembly, and use. 

2. Methods and Materials 

1. Grant W-38 Thermostatic Circulated Bath (calibrated) 

2. 5% NaCl solution 

3. Four thermometers (calibrated) 

4. Fluke 289 True RMS multimeter 

3. Test Candidates 

The test candidates consisted of grade-10.9 13-mm hexavalent bolts, nuts, and washers. 

1. Bare 4340 steel. 

2. Control: ASTM B 633 electroplated zinc with hexavalent chromium conversion coating. 

3. Trivalent chrome plating (TCP): ASTM B 633 electroplated zinc with trivalent chromium 

conversion coating. 

4. AlumiPlate (AlumiPlate, Inc.) process details: Entire surface was electroplated with Al 

alloy 1199 at 99.99% pure and conversion coated with Metalast TCP, then the threaded 

areas were coated in accordance with MIL-PRF-46010 solid film lubricant (Everlube 

9002). 
2

5. Magni 565 (MagniGroup, Inc.) process details: Entire surface was coated with inorganic, 

zinc-rich coating, and topcoated with an Al-rich organic topcoat. 

6. Magni 594 (MagniGroup, Inc.) process details: Entire surface was coated with inorganic 

zinc coating and topcoated with a friction-modified, organic Al-rich coating. 

4. Experimental Procedure 

1. Each bolt had a 1/8-in hole bored into the center of its head (see figure 1). 

2. A Zn-plated steel screw, wrapped with wire, was fixed in place using this hole. 

3. Polysulfide sealant was used to insulate and seal the wire/screw assembly to the bolt to 

prevent contamination (see figure 2 for full assembly). 

4. A thermostatic circulated bath was filled with a 5% NaCl solution and heated to 75 °F. 

Solution temperature was maintained for the duration of the experiment, and the water was 

continually agitated. 

5. Two of each specimen were immersed in the bath for 500 h. Open circuit potential 

measurements and visual inspections were taken after 1, 2, 4, 8, and 24 h, and every 24 h 

thereafter. 

Figure 1. Bolt/screw assembly. 
3

Figure 2. (a) Prepared bolts prior to immersion and (b) immersion bath setup. 

5. Results and Discussion 

With respect to cosmetic corrosion, the TCP/zinc-treated bolts corroded at a faster rate than bare 

steel. Bare steel and TCP/zinc were the only two bolt types that corroded faster than hexavalent 

chrome/zinc, as AlumiPlate and both types of MagniPlate experienced significantly less 

corrosion (figure 3). After the 500-h immersion, only the bare steel and TCP/zinc bolts ever 

reached 100% surface area corrosion. The open circuit potential of each bolt was also measured 

and recorded throughout the course of the immersion experiment. As can be seen in figure 4, the 

bare steel provided a baseline of about 0.68 V. With the exception of MagniPlate 594, all the 

treated bolt specimens made it to 120 h without a significant change in open circuit potential. 

MagniPlate 594 immediately dropped in voltage and eventually ended up at the same potential as 

that of bare steel. AlumiPlate and MagniPlate 565 both experienced drops in potential after 

120 h, though not nearly as severe as that of MagniPlate 594, and finished out the immersion 

period at 0.7755 and 0.8498 V, respectively. Despite the appearance of immediate cosmetic 

corrosion, TCP/zinc did not show signs of any change in potential until after 250 h of immersion. 

At this point, the drop-off in potential dropped drastically and never leveled out prior to the end 

of the experiment. Photos of the bolts after being removed from the solution can be seen in 

figures 5–10, while scans of the dried bolts can be seen in figures 11 and 12. Although the open 

circuit potential of the hexavalent chrome/zinc bolts remained high throughout the experiment, 

the bolts appeared to have lost their protective coating and showed a significant amount of steel 

corrosion. 

(a) (b) 
4

Figure 3. Visual corrosion on immersed bolts.

Figure 4. Open circuit potential of immersed bolts. 
5

Figure 5. Bare bolts immediately after immersion. 

Figure 6. Hexavalent chrome/zinc bolts immediately 

after immersion. 

Figure 7. TCP/zinc bolts immediately after immersion. 
6

Figure 8. AlumiPlate bolts immediately after immersion. 

Figure 9. MagniPlate 565 immediately after immersion. 

Figure 10. MagniPlate 594 immediately after immersion.
7

Figure 11. Bare steel, hexavalent 

chrome/zinc, and 

TCP/zinc after drying. 
8

Figure 12. AlumiPlate, MagniPlate 565, 

and MagniPlate 594 after 

drying.
9

With respect given to the original experimental setup and aided by a wealth of extra bolts, it was 

decided by a team of engineers to try the experiment a second time. This second experiment 

would be set up just as the first but with each bolt type isolated from each other so as to prevent 

cross-contamination. Pyrex glass jars were filled with a 5% salt solution and fitted with an 

agitation system using clean, dry air to circulate the water. The glass jars sat in the same water 

bath and were heated to 75 °F for 500 h. The results of this supplementary experiment are 

shown in figures 13–22. Unlike the original setup, the hexavalent chrome/zinc bolts did not 

show any signs of coating loss or steel corrosion. Visible corrosion was also different in that the 

TCP and bare 4340 bolts corroded quickly and heavily, whereas the other bolts experienced 

much less corrosion, none of which ever exceeded 10%. The open circuit potential readings 

were not as stable as before, as all bolt specimens tested experienced a drop-off after 250 h. 

Figure 13. Visual corrosion on immersed bolts in supplementary experiment. 
10

Figure 14. Open circuit potential of immersed bolts in supplementary experiment. 

Figure 15. Bare bolts immediately after immersion in 

supplementary experiment. 
11

Figure 16. Hexavalent chrome/zinc bolts immediately 

after immersion in supplementary 

experiment. 

Figure 17. TCP/zinc bolts immediately after immersion 

in supplementary experiment. 

Figure 18. AlumiPlate bolts immediately after 

immersion in supplementary experiment. 
12

Figure 19. MagniPlate 565 immediately after immersion 

in supplementary experiment. 

Figure 20. MagniPlate 594 immediately after immersion 

in supplementary experiment.
13

Figure 21. Bare steel, hexavalent 

chrome/zinc, and TCP/zinc 

after drying in 

supplementary experiment. 
14

Figure 22. AlumiPlate, MagniPlate 565, 

and MagniPlate 594 after 

drying in supplementary 

experiment. 
15

6. Conclusions 

• MagniPlate 565 and 594 had the least visible corrosion. 

• MagniPlate 565 and 594, and AlumiPlate experienced less corrosion than the baseline 

hexavalent chrome/zinc. 

• Aside from hexavalent chrome/zinc, which maintained essentially the same open circuit 

potential throughout the experiment, MagniPlate 565 maintained the second-highest 

potential with respect to the baseline given by the bare steel bolts. 

• The TCP/zinc used should be given further analysis in order to explain its poor 

performance. 

• Additional studies should be done to examine the compatibility of MagniPlate 565 and 594, 

and AlumiPlate with existing armor systems. 
NO. OF 

COPIES ORGANIZATION 

16

 1 DEFENSE TECHNICAL 

 (PDF INFORMATION CTR 

 only) DTIC OCA 

 8725 JOHN J KINGMAN RD 

 STE 0944 

 FORT BELVOIR VA 22060-6218 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 IMNE ALC HRR 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 RDRL CIM L 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 RDRL CIM P 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

 1 DIRECTOR 

 US ARMY RESEARCH LAB 

 RDRL D 

 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

ABERDEEN PROVING GROUND

 1 DIR USARL 

 RDRL CIM G (BLDG 4600)