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Corrosion Resistance of DuraBeryllium Plus X-ray Windows Part 1

By Mallorie Harker · App and Tech Notes · 25/03/14

DuraBeryllium X-ray window

DuraBeryllium Plus X-ray window

DuraBeryllium® Plus windows are Moxtek’s most robust coated beryllium x-ray window. This window has an additional thin coating of polymer “Plus” applied to the already robust DuraBeryllium window. The Plus layer is more resistant to water and other harsh chemicals.
DuraBeryllium Plus windows successfully withstand continuous exposure to heated water as well as to other chemicals. A series of tests were completed on DuraBeryllium windows as seen in the test summary below. Part 1 of this application note details exposure of DuraBeryllium Plus to water, KOH, and HCl. Part 2 will be released later in 2012 and will include details of exposure of this window to other harsh chemicals.

X-ray Transmission

DuraBeryllium protective layers provide corrosive shielding as well as a hermetic barrier to the beryllium foil. These protective
layers are very thin and the resulting x-ray attenuation is equivalent to about 1μm of beryllium, having little impact on x-ray
transmission. See chart below.

corrosion resistance part1 1

Pressure and Thermal Cycling

To demonstrate strength of the DuraBeryllium window, Moxtek pressure and thermal cycled thirty mounted windows. All thirty mounted windows were exposed to 10,000 cycles (15psi to atmosphere). Ten of these endcaps went through an additional 10,000 cycles. All windows withstood the pressure and thermal cycling without failure. The flowchart below details the testing procedure used.

corrosion resistance part1 2

Pressure and Thermal Cycling Testing Flow Chart
* Pass if helium leak tight <1.00 x 10-10 (mbar * L/sec)

Corrosion Resistance

8μm DuraBeryllium windows are very robust when continuously exposed to water at both room temperature and at 65º C. Conversely uncoated 8 μm beryllium windows will corrode when exposed to water within days. The flowchart below details the testing procedure used.

corrosion resistance part1 3

* Pass if helium leak tight <1.00 x 10-10 (mbar * L/sec)

DuraBeryllium When Exposed to Water

The table below shows the robustness of DuraBeryllium windows when exposed to water.

Pass (P) = He Leak Tight (<1 x 10-10
mbar * L/sec)
Leak Testing
~60°C H2ORoom Temperature H2O
DuraBeryllium PlusDuraBerylliumDuraBeryllium PlusDuraBeryllium
Approx. Time ExposureA0177A0156V311miscA0159A0174A0168A0166A01533D4DV3112
3 hoursPPPPP
4 hoursPPP
5 hoursPPP
10 hoursPPPPPP
15 hoursPP
20 hoursPPPPP
24 hoursPPP
2 daysPPPPPPPPP
3 daysPPP
4 daysPPPPPPPPP
6 daysPPPPP
7 daysPPP
8 daysPP
11 daysPPPPPPPP
14 daysPPPPP
18 daysPPPPPPP
21 daysPPPPP
1 monthPPPPPPPPPPPP
2 monthPPPPPPPPPPPP
3 monthPPPPPPPPPPPP
4 monthPPPPPPPPPXFailP
5 monthPPPPPPPPPP
6 monthPPPPPPPPPP
Blank box= no data collected. X= damaged.

Visual Observation

The images below were taken four months after exposure to H2O at room temperature. As seen in the images, there was some discoloration on the window coating but all windows were leak tight.

corrosion resistance part1 4

Note: Corrosion observed on only 2 of the 7 DuraCoat Plus endcaps

KOH Exposure Test (Exposure = 1 week)

Under extreme KOH exposure for one week, DuraBeryllium Plus did not develop any leaks. Some visual polymer delamination was observed after 6 days. Prolonged exposure to KOH will eventually dissolve the polymer “Plus” layer.

Leak Testing Results
10% KOH
Time ExposureDuraBeryllium PlusDuraBeryllium
A0172A0154no number
3 hoursPPP
4 hoursPP-
5 hours---
6 hoursPPP
10 hoursPP-
15 hoursPP-
20 hours---
24 hours--P
2 daysPP-
3 days--P
4 days--P
6 daysPP
7 daysPP
10% KOH Exposure at room temp

HCl Exposure Text (Exposure = 1 week)

HCl reacts quickly with bare beryllium and corrodes 8μm Be windows within minutes. Both DuraBeryllium Plus and DuraBeryllium add some resistance to this harsh chemical but only for a few hours, as seen in the table below.

Leak Testing Results
10% HCl
Time ExposureDuraBeryllium PlusDuraBeryllium
A0160A0179misc
3 hoursFPF
3 hoursF
corrosion resistance part1 5

DuraBeryllium® Plus and DuraBeryllium®
Visual image above of DuraBeryllium Plus and
DuraBeryllium after exposure to 10% HCl at room temperature for ~3 hours. HCl
speedily reacts under the surface of DuraBeryllium.

DuraBeryllium Plus and DuraBeryllium Visual image above of DuraBeryllium Plus and DuraBeryllium after exposure to HCl for ~3 hours. HCl speedily reacts under the surface of DuraBeryllium.

Conclusion

Corrosion Resistance:
DuraBeryllium Plus windows demonstrate remarkable resistance to corrosion after prolonged exposure to heated water. Corrosion on DuraBeryllium Plus windows is minimal and delimitation is non-existent after continuous exposure times of over 6 months without any windows developing a leak.
DuraBeryllium Plus windows are affected by exposure of HCl. This chemical will slowly dissolve the outer polymer layer but the beryllium window will still be protected by the inner DuraCoat layer. More testing will be completed at Moxtek to determine resistivity of the DuraCoat to this chemical and will be reported in a later application note.
HCl reacts quickly with bare beryllium and corrodes through a 8μm Be foil within minutes. Both DuraBeryllium Plus and DuraBeryllium add some resistance to this harsh chemical but only for a few hours.
X-ray Transmission:
DuraCoat Plus layers are applied to all Moxtek 8μm thick DuraBeryllium Plus window. The DuraCoat Plus layers consist of very thin layers of DuraCoat and polymer. These protective layers are very thin, and have little impact on x-ray transmission.

Recommendation

DuraBeryllium and DuraBerylllium Plus windows are recommended for all applications that require 8μm thick beryllium windows.

 

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