Corrosion Testing
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Transcript Corrosion Testing
Corrosion Testing
Acknowledgements to:
Paul Natishan, Rick Foster, CAPT Marty Mahon
Center for Corrosion Science & Engineering
Naval Research Laboratory
Washington, DC and Key West, FL
Atmospheric Corrosion Testing
Substrate Materials: 4340 steel
Substrate Preparation: For EHC, grit blast with 180-220 grit Al2O3
For HVOF, grit blast with 54 grit Al2O3
Coating Deposition:
EHC deposited following MIL-STD-1501
WC/17Co deposited using hybrid Diamondjet gun, hydrogen fuel,
Diamalloy 2005 powder
Tribaloy 400 deposited using Jet Kote II, hydrogen fuel, Stellite T-400
powder
Coating thicknesses of 0.004 inches
Tested as-deposited (no grinding)
Epoxy masking used on non-coated surfaces
HVOF and Hard Chrome Coatings on 4340 Steel
Atmospheric Exposure For 3 Years
Thickness 0.004”, Coatings Not Ground
PROTECTION RATINGS FOR 4 MIL COATINGS OVER 4340 STEEL (PLATES)
Edge
Hard Chrome, with nickel
sublayer
Face
Triballoy 400 **
WC/Co *
0
2
4
6
8
Protection Ratings (10 = Best)
** "T-400" (Stellite): 60% Co, 28% Mo, 9% Cr, 3% Si
* Diamalloy 2005 (Sulzer-Metco): 83%WC, 17% Co
10
12
Additional Corrosion Testing
To address significant discrepancy between previous B117 and atmospheric
testing on flat plates, and LG B117 testing on rods, additional B117
corrosion tests were conducted as follows:
Substrate Materials:
4340 rods, 1” diameter, 6” long
4340 plates, 3” x 4” x 3/16”
300M rods, 1” diameter, 6” long
Coatings:
WC/17Co, WC/10Co4Cr, EHC
On rods, coatings to be applied on curved surface, terminating 1” from one end
and 1/4” from other end (length of coating 4-3/4 inches)
On plates, only coat one face 3”-wide dimension coated edge-to-edge, on 4”-wide
dimension, coating to terminate 1/2-inch from edge (coated area is 3” x 3”)
Deposition parameters to match Landing Gear JTP, plus must follow Boeing
Spec. Sheet 160T1000 which requires that HVOF coatings not terminate with
a square edge, but shall taper from full to zero thickness over a minimum
length of 0.006 inches
EHC coatings ground to 16 Ra finish; some HVOF coatings ground to 8 Ra
Non-coated areas to be cadmium plated (including chromate conversion
coating) with slight overlap of EHC and HVOF coating
Additional Corrosion Testing
4340 rods
Coating
WC/Co
WC/Co
WC/Co
WC/Co
WC/Co
WC/Co
WC/CoCr
WC/CoCr
WC/CoCr
WC/CoCr
WC/CoCr
WC/CoCr
EHC
EHC
Thickness Ground
0.003”
0.003”
0.003”
0.003”
0.010”
0.010”
0.003”
0.003”
0.003”
0.003”
0.010”
0.010”
0.003”
0.010”
Spray Co. # of samples
Y
Y
N
N
Y
Y
Y
Y
N
N
Y
Y
Y
Y
Hitemco
Southwest
H
S
H
S
H
S
H
S
H
S
S
S
Total
Repeat this exact matrix for the 4340 plates and the 300M rods.
2
2
2
2
2
2
2
2
2
2
2
2
2
2
28
breached
coating
August 2000
August 2001
WC/Co coatings (ground) on 300M steel.
breached
coating
August 2000
August 2001
WC/Co coatings (ground) on 4340 steel.
breached
coating
August 2000
August 2001
Comparison of hard chrome samples.
Type 300M Metal Coating Appearance Ratings
EHC 10 Gr SWAero
EHC 3 Gr SWAero
WC/Co/Cr 10 Gr SWAero
WC/Co/Cr 10 Gr Hitem
WC/Co/Cr 3 UG SWAero
Coating Type
WC/Co/Cr 3 UG Hitem
WC/Co/Cr 3 Gr SwAero
Series2
Series1
WC/Co/Cr 3 Gr Hitem
WC/Co 10 Gr SWAero
WC/Co 10 Gr Hitem
WC/Co 3 UG SWAero
WC/Co 3 UG Hitem
WC/Co 3 Gr SWAero
WC/Co 3 Gr Hitem
0
2
4
6
Appearance Rating
8
10
12
Type 4340 Metal Coating Appearance Ratings
EHC 10 Gr SWAero
EHC 3 Gr SWAero
WC/Co/Cr 10 Gr Hitem
WC/Co/Cr 3 UG SWAero
Coating Type
WC/Co/Cr 3 UG Hitem
WC/Co/Cr 3 Gr SwAero
Series2
Series1
WC/Co/Cr 3 Gr Hitem
WC/Co 10 Gr SWAero
WC/Co 10 Gr Hitem
WC/Co 3 UG SWAero
WC/Co 3 UG Hitem
WC/Co 3 Gr SWAero
WC/Co 3 Gr Hitem
0
2
4
6
Appearance Rating
8
10
12
general
breached
coating
corrosion
unground
ground
WC/Co coatings (3 mil) on 4340 steel.
general
corrosion
WC/Co
ground
10 mil
EHC
ground
10 mil
WC/Co-Cr
ground
10 mil
Comparison of HVOF and EHC coatings on 4340 steel.
general
corrosion
WC/Co
ground
10 mil
EHC
ground
10 mil
WC/Co-Cr
ground
10 mil
Comparison of HVOF and EHC coatings on 300M steel.
general
general
corrosion
breached
coating
unground
corrosion
ground
WC/Co coatings (3 mil) on 300M steel.
general
breached
coating
corrosion
ground
3 mil
ground
10 mil
WC/Co coatings on 4340 steel.
general
corrosion
general
breached
coating
corrosion
ground
3 mil
ground
10 mil
WC/Co coatings on 300M steel.
general
corrosion
EHC
10 mil
WC/Co
ground
10 mil
Comparison of HVOF and EHC coatings on 4340 steel.
general
corrosion
EHC
10 mil
WC/Co
ground
10 mil
Comparison of HVOF and EHC coatings on 300M steel.
SUMMARY OF CORROSION TESTING
10 mil thick coatings fared better than 3 mil coatings of any
composition in protecting the substrate.
The company applying the coating does not have a measurable,
definitive effect on coating performance (given the small sample set).
Salt fog cabinet used at Kennedy Space Center appeared to be slightly
more aggressive than one used at Naval Research Laboratory
EHC coatings outperform all other coating compositions, regardless of
thickness in this year’s B117 test.
At 10 mil thickness, the data set infers WC/CoCr coatings show
improved performance over WC/Co coatings, though one 10 mil
WC/Co-Cr coating was breached.