1. Testing SILSBOND
on Aluminum
Alloys
By Trevor Yates

2. Aluminum Alloys
 Aluminum used widely in the aircraft industry due to its
wear resistance and tensile strength
 For over fifty years hexavalent chromium has been used
as a corrosion-inhibiting compound for the protection of
metal surfaces
 Hexavalent chromium currently is the best performing
pretreatment solution available for aluminum

3. Cr (VI) Toxicity
 Hexavalent Chromium recognized as a human
carcinogen
 European Union restricts use in electronic equipment by
Restriction of Hazardous Substances Directive
 OR-OSHA adopted regulations to protect workers
exposed to Chromium (VI) in the workplace 52 ug/m^3

4. SILSBOND
• Nano-films
• Excellent adhesion and corrosion protection for
aluminum and galvanized steel and cold rolled steel
• Reduces process steps

5. Objectives
 Test SILSBOND against Alodine 1200 and 4200
 Optimize process parameters
 Test new formulas modified to compete against SILSBOND 01
and 02 and 03
 Provide results and conclusions to NSF in order to contribute to
their overall goal of limiting Cr 6 use on aircraft aluminum

6. Procedure
 Al 7075 and 2024 and 6061
Military Paints: MIL-PRE-53022D and MIL-PRE-53022E and
MIL-PRE-23377J
 1st Round: SILS01 3%+1.5% vs. 4200 3% pH 4.5 and
Alodine 1200 and Untreated
 2nd Round: SILS01 vs. SILS02 vs. SILS03
 3rd Round: SILS02 vs. A21 and A22
 Immersion
 Apply paint via pressurized air until desired thickness
achieved
 Cure 80 degrees Celsius for 30 minutes
 CASST chamber 240 hours and SST 500 hours

7. Testing Parameters
 Concentration (1.5 % and 3 % and 5%)
 Immersion time (60 seconds and 90 seconds and 120
seconds)
 Immersion temperature
(RT and 105-110 F and 115-120 F and 125-130 F)
 Baking (NONE and 80 C for 5 minutes and 20
minutes)

8. Copper-Accelerated Acetic Acid
Salt Spray Test

9. Specific Testing Conditions
 Chamber interior 49 Celsius and DIW 63 Celsius
 95 parts water and 5 parts sodium chloride
 0.25 gram reagent grade copper chloride per liter of
solution
 pH adjusted between 3.1-3.3 with acetic acid
 Flow rate 1.0-2.0 mL/hr and pressure 16 psi
 DIW placed on bottom floor to prevent cracking of
material from thermal expansion

10. Salt Spray Test

11. Specific Testing Conditions
 Chamber interior 35 Celsius and DIW 50 Celsius
 95 parts DIW and 5 parts sodium chloride
 pH must be between 6.5-7.2
 Specific gravity 1.02-1.04
 Flow rate 1.0-2.0 mL/hr and pressure 17-18 psi

12. Average Delamintaion (mm) 1st
Round Salt Spray Test Al 2024

13. Average Delamintation (mm) 1st
Round CASS Chamber Test Al 2024
0
1
2
3
4
5
6
7
MIL-PRE-53022D MIL-PRE53022E
SILS 01 1.5%
SILS 01 3%
Alodine
1200
Untreated
4200

14. 2nd Round CASS Test
SILS 01 3% 2 days SILS 02 3% 5 days SILS 03 3% 2 days

15. Best Performers
Alodine 1200 9 days SILS 02 3% 115-120 F 9 days

16. 3rd Round CASS Test (9 days)
4200 3% RINSE 4200 3% NO RINSE

17. 3rd Round CASS Test Continued
SILS 02 1.5% SILS 02 3% SILS 02 5%
WORSTBEST

18. 3rd Round CASS Test Continued
 BEST
A22 1.5% A22 3% A22 5%
WORSTBEST

19. Overall 9 Days Comparison
a b c
d
a.) A22 1.5%
b.) 4200 RINSE
c.) SILS 02 1.5%
d.) Alodine 1200

20. Further Investigate
 Optimize A22
 1.5 % concentration sweet spot
 125-130 F Immersion temperature sweet spot
 Post baking helps 80 C for 20 minutes