WO2004077603A1 - Corrosion resistant waveguide system and method of realizing the same - Google Patents

Corrosion resistant waveguide system and method of realizing the same Download PDF

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Publication number
WO2004077603A1
WO2004077603A1 PCT/US2004/002428 US2004002428W WO2004077603A1 WO 2004077603 A1 WO2004077603 A1 WO 2004077603A1 US 2004002428 W US2004002428 W US 2004002428W WO 2004077603 A1 WO2004077603 A1 WO 2004077603A1
Authority
WO
WIPO (PCT)
Prior art keywords
waveguide device
coating
aluminum coating
aluminum
deposited
Prior art date
Application number
PCT/US2004/002428
Other languages
French (fr)
Inventor
Mel V. Huynh
Carl W. Townsend
Philip G. Magallanes
Original Assignee
Raytheon Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Raytheon Company filed Critical Raytheon Company
Priority to DE602004016824T priority Critical patent/DE602004016824D1/en
Priority to EP04706463A priority patent/EP1597792B1/en
Publication of WO2004077603A1 publication Critical patent/WO2004077603A1/en
Priority to NO20054146A priority patent/NO20054146L/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P11/00—Apparatus or processes specially adapted for manufacturing waveguides or resonators, lines, or other devices of the waveguide type
    • H01P11/001—Manufacturing waveguides or transmission lines of the waveguide type
    • H01P11/002—Manufacturing hollow waveguides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P11/00—Apparatus or processes specially adapted for manufacturing waveguides or resonators, lines, or other devices of the waveguide type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P3/00—Waveguides; Transmission lines of the waveguide type
    • H01P3/12—Hollow waveguides

Definitions

  • the disclosure is generally directed to microwave waveguide devices, and more particularly to techniques for reducing corrosion due to electrical arcing.
  • Microwave waveguide devices are employed in variety of applications such as radar and RF communications. Waveguide devices are typically formed of metal, and electrical arcing can occur, for example at relatively high power levels. Arcing is believed to cause corrosion of the interior surfaces of waveguide devices, and corrosion product buildup can subsequently cause failure.
  • the disclosed waveguide device includes a waveguide device body having an interior surface, a deposited aluminum coating deposited on the interior surface of the waveguide device body, a protective coating deposited on the deposited aluminum coating.
  • FIG. 1 is a schematic perspective view of an embodiment of a waveguide device that includes interior surfaces having a protective coating.
  • FIG. 2 is a schematic sectional view of the waveguide device of FIG. 1.
  • FIG. 3 is a flow diagram of an embodiment of a process for making a waveguide device having coated interior surfaces.
  • the disclosed waveguide device structures include a composite coating that can help to reduce corrosion that is believed to result from arcing.
  • the corrosion product found in aluminum waveguides is primarily aluminum nitrate, and is believed to be formed by an arcing process, with nitric acid as an intermediate product. Chemically, the process can be summarized as three sequential chemical reactions:
  • Aluminum waveguides have in the past been coated with chromate conversion coating. However, the interior surfaces were relatively rough. At high power levels, arcing is initiated on protruding surfaces, typically rough areas at braze joints. Arcing in turn causes the formation of nitric acid. The nitric acid attacks first the chromate film, and subsequently the aluminum surface. Corrosion product buildup can subsequently cause failure of rotating components such as waveguide switches.
  • the disclosed composite coating which comprises deposited aluminum coating and an overlying chromate conversion coating are believed to protect the waveguide device body from the nitric acid.
  • FIG. 1 is a schematic perspective view and FIG. 2 is a sectional view of an embodiment of a waveguide device 11 that includes an energy conducting portion 11a and a connector portion 1 lb.
  • the energy conducting portion 11a can comprise a waveguide section, for example, while the connector portion 1 lb can comprise a flange that is attached to the guide section by brazed solder joints lie, for example.
  • the solder joints lie can be smoothed by electropolishing, mechanical polishing and/or chemical milling.
  • the waveguide device 11 more particularly includes a body 21 having interior surfaces 21a.
  • the body 21 can be formed of any suitable waveguide material such as type 6061 aluminum, for example.
  • a deposited aluminum layer or coating 23 is disposed on the interior surfaces 21a and at least those portions of the solder joints l ie that would be in the interior of the waveguide circuit in which the waveguide device 11 is utilized. More generally, the deposited aluminum coating can be on surfaces of the waveguide device that would otherwise be subjected to electrical arcing generated nitric acid in the absence of the deposited aluminum coating 23.
  • the deposited aluminum coating 23 can have a thickness in the range of 0.0001 inch to about 0.002 inch. By way of specific example, the deposited aluminum coating can have a thickness of about 0.0016 inches.
  • a chromate conversion coating 25 is disposed on the deposited aluminum coating 23.
  • the aluminum coating 23 and the chromate conversion coating 25 comprise a composite protective coating that can reduce corrosion of the waveguide device body caused by electrical arcing.
  • the deposited aluminum layer e.g. deposited using an ion vapor deposition process, has the advantage that it substantially matches the galvanic potential of 6061 aluminum, and the conversion film seems to effectively fill the porosity of the alummum layer, both shutting off the point of exposure and providing a significant reservoir of additional chromate material.
  • FIG. 3 is a flow diagram of an embodiment of a process for making a coated waveguide device such as those illustrated in FIGS. 1 and 2.
  • interior surfaces of a waveguide device body are smoothed, for example by electropolishing, mechanical polishing and/or chemical milling. Such smoothing can reduce arcing.
  • an aluminum coating is deposited on interior surfaces of the waveguide device body, for example by ion vapor deposition. Other techniques such as electroplated aluminum can alternately be employed, although ion vapor deposition is a preferred technique.
  • the aluminum coating 23 can also be deposited on solder regions as deemed appropriate.
  • a chromate conversion coating is applied over at least the aluminum coating.
  • the chromate conversion coating can be applied over the entire microwave device by immersion in a chromic acid solution, as is known in the art.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physical Vapour Deposition (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)

Abstract

A waveguide device (11) that includes a waveguide device body (21) having interior surfaces (21a), a deposited aluminum coating (23) disposed on the interior surfaces of the waveguide device body, a protective chromate conversion coating (25) disposed on the deposited aluminum coating.

Description

CORROSION RESISTANT COATED WAVEGUIDE ND METHOD OF REALIZING HE SAME
TECHNICAL FIELD OF THE DISCLOSURE
[0001] The disclosure is generally directed to microwave waveguide devices, and more particularly to techniques for reducing corrosion due to electrical arcing.
BACKGROUND OF THE DISCLOSURE
[0002] Microwave waveguide devices are employed in variety of applications such as radar and RF communications. Waveguide devices are typically formed of metal, and electrical arcing can occur, for example at relatively high power levels. Arcing is believed to cause corrosion of the interior surfaces of waveguide devices, and corrosion product buildup can subsequently cause failure.
[0003] Accordingly, there is a need to reduce corrosion in waveguide devices.
SUMMARY OF THE DISCLOSURE
[0004] The disclosed waveguide device includes a waveguide device body having an interior surface, a deposited aluminum coating deposited on the interior surface of the waveguide device body, a protective coating deposited on the deposited aluminum coating. BRIEF DESCRIPTION OF THE DRAWING
[0005] Features and advantages of the disclosure will become more apparent from the following detailed description of exemplary embodiments, as illustrated in the accompanying drawings, in which:
[0006] FIG. 1 is a schematic perspective view of an embodiment of a waveguide device that includes interior surfaces having a protective coating.
[0007] FIG. 2 is a schematic sectional view of the waveguide device of FIG. 1.
[0008] FIG. 3 is a flow diagram of an embodiment of a process for making a waveguide device having coated interior surfaces.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0009] The disclosed waveguide device structures include a composite coating that can help to reduce corrosion that is believed to result from arcing. The corrosion product found in aluminum waveguides is primarily aluminum nitrate, and is believed to be formed by an arcing process, with nitric acid as an intermediate product. Chemically, the process can be summarized as three sequential chemical reactions:
1) Nitrogen Fixing: 202 + N2 + arc 2N02
2) Acid Formation: 3N02 + H20 2HN03 + N0
3) Corrosion: Al + 6HNO3 + xH20 A1(N03)3 * (x+3)H20 + 3N02
[0010] Aluminum waveguides have in the past been coated with chromate conversion coating. However, the interior surfaces were relatively rough. At high power levels, arcing is initiated on protruding surfaces, typically rough areas at braze joints. Arcing in turn causes the formation of nitric acid. The nitric acid attacks first the chromate film, and subsequently the aluminum surface. Corrosion product buildup can subsequently cause failure of rotating components such as waveguide switches.
[0011] Prior attempts to solve the problem have included the use of silver or gold plating to enhance the corrosion protection while simultaneously improving conduction of microwave energy. Since silver is rapidly attacked by nitric acid, these systems are prone to corrosion. Due to its high galvanic mismatch with aluminum, gold plating initiates undercutting in pinhole defects.
[0012] The disclosed composite coating which comprises deposited aluminum coating and an overlying chromate conversion coating are believed to protect the waveguide device body from the nitric acid.
[0013] FIG. 1 is a schematic perspective view and FIG. 2 is a sectional view of an embodiment of a waveguide device 11 that includes an energy conducting portion 11a and a connector portion 1 lb. The energy conducting portion 11a can comprise a waveguide section, for example, while the connector portion 1 lb can comprise a flange that is attached to the guide section by brazed solder joints lie, for example. The solder joints lie can be smoothed by electropolishing, mechanical polishing and/or chemical milling.
[0014] The waveguide device 11 more particularly includes a body 21 having interior surfaces 21a. The body 21 can be formed of any suitable waveguide material such as type 6061 aluminum, for example. A deposited aluminum layer or coating 23 is disposed on the interior surfaces 21a and at least those portions of the solder joints l ie that would be in the interior of the waveguide circuit in which the waveguide device 11 is utilized. More generally, the deposited aluminum coating can be on surfaces of the waveguide device that would otherwise be subjected to electrical arcing generated nitric acid in the absence of the deposited aluminum coating 23. The deposited aluminum coating 23 can have a thickness in the range of 0.0001 inch to about 0.002 inch. By way of specific example, the deposited aluminum coating can have a thickness of about 0.0016 inches. A chromate conversion coating 25 is disposed on the deposited aluminum coating 23.
[0015] The aluminum coating 23 and the chromate conversion coating 25 comprise a composite protective coating that can reduce corrosion of the waveguide device body caused by electrical arcing. The deposited aluminum layer, e.g. deposited using an ion vapor deposition process, has the advantage that it substantially matches the galvanic potential of 6061 aluminum, and the conversion film seems to effectively fill the porosity of the alummum layer, both shutting off the point of exposure and providing a significant reservoir of additional chromate material.
[0016] FIG. 3 is a flow diagram of an embodiment of a process for making a coated waveguide device such as those illustrated in FIGS. 1 and 2. At 121 interior surfaces of a waveguide device body are smoothed, for example by electropolishing, mechanical polishing and/or chemical milling. Such smoothing can reduce arcing. At 123 an aluminum coating is deposited on interior surfaces of the waveguide device body, for example by ion vapor deposition. Other techniques such as electroplated aluminum can alternately be employed, although ion vapor deposition is a preferred technique. The aluminum coating 23 can also be deposited on solder regions as deemed appropriate.
[0017] At 125 a chromate conversion coating is applied over at least the aluminum coating. For example, the chromate conversion coating can be applied over the entire microwave device by immersion in a chromic acid solution, as is known in the art.
[0018] In use, damage and/or corrosion due to electrical arcing can be further reduced by operating the waveguide device in conditions that reduce arcing. For example, lower power levels have been observed to reduce arcing. Also, since the corrosive arcing process described previously requires water to form nitric acid, reducing humidity in a waveguide device could reduce the formation of nitric acid which in turn would reduce corrosion. This could be done by circulating dry gas within the entire waveguide structure, or by desiccation. [0019] It is understood that the above-described embodiments are merely illustrative of the possible specific embodiments which may represent principles of the present invention. Other arrangements may readily be devised in accordance with these principles by those skilled in the art without departing from the scope and spirit of the invention.

Claims

CLAIMSWhat is claimed is:
1. A waveguide device (11) comprising: a waveguide device body (21) having an interior surface (21a); a deposited aluminum coating (23) disposed on said interior surface; and a protective coating (25) disposed on said deposited aluminum coating.
2. A waveguide device according to Claim 1 wherein said deposited aluminum coating (23) comprises a vapor deposited aluminum coating.
3. A waveguide device according to Claim 1 wherein said protective coating (25) comprises a chromate conversion coating.
4. A waveguide device according to any preceding claim wherein said waveguide device body (21) is fabricated of 6061 alummum.
5. A method of making a waveguide device (11) comprising: depositing an aluminum coating (23) on an interior surface of a waveguide device body (21); and applying a protective coating (25) on the deposited aluminum coating.
6. A method according to Claim 5 wherein depositing an aluminum coating (25) comprises vapor depositing an aluminum coating on an interior surface (21a) of the waveguide device body.
7. A method according to Claim 5 or Claim 6 wherein applying a protective coating (25) comprises chromate conversion coating the deposited aluminum coating.
8. A method according to any of Claims 5-7 wherein the waveguide device is fabricated of 6061 aluminum.
9. A method according to any of Claims 5-8, further comprising: smoothing solder joints (1 lc) of a waveguide device body prior to said depositing an aluminum coating.
10. A method according to Claim 9 wherein said smoothing solder joints comprises smoothing braze joints.
11. A waveguide device made in accordance with the method of any of Claims 5-10.
12. A method of reducing corrosion of a waveguide device (11) comprising: depositing an aluminum coating (23) on selected surfaces (21a) of a waveguide device body (21); applying a protective coating (23) on the deposited aluminum coating; and operating the waveguide device at electrical power conditions that reduce arcing.
13. A method according to Claim 12 further including reducing humidity in the waveguide device.
14. A method according to Claim 12 or Claim 13 wherein said applying a protective coating comprises applying a chromate conversion coating.
15. A method according to Claim 14 wherein the waveguide device is fabricated of aluminum.
PCT/US2004/002428 2003-02-26 2004-01-29 Corrosion resistant waveguide system and method of realizing the same WO2004077603A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE602004016824T DE602004016824D1 (en) 2003-02-26 2004-01-29 HREN TO ITS REALIZATION
EP04706463A EP1597792B1 (en) 2003-02-26 2004-01-29 Corrosion resistant waveguide system and method of realizing the same
NO20054146A NO20054146L (en) 2003-02-26 2005-09-06 Corrosion-resistant waveguide system and method for making the same

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US10/375,311 2003-02-26
US10/375,311 US6927654B2 (en) 2003-02-26 2003-02-26 Corrosion resistant waveguide system and method

Publications (1)

Publication Number Publication Date
WO2004077603A1 true WO2004077603A1 (en) 2004-09-10

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US (1) US6927654B2 (en)
EP (1) EP1597792B1 (en)
KR (1) KR100680082B1 (en)
DE (1) DE602004016824D1 (en)
NO (1) NO20054146L (en)
WO (1) WO2004077603A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004003010A1 (en) * 2004-01-20 2005-08-04 Endress + Hauser Gmbh + Co. Kg Microwave conducting arrangement
KR102438369B1 (en) * 2020-12-04 2022-08-31 성균관대학교산학협력단 Waveguide for near field measurement

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60246104A (en) * 1984-05-22 1985-12-05 Showa Denko Kk Cylindrical radio wave reflecting tube
EP0210543B1 (en) * 1985-08-02 1994-03-02 Texas Instruments Incorporated Radar rotary joint
US6265703B1 (en) * 2000-06-02 2001-07-24 The Ferrite Company, Inc. Arc suppression in waveguide using vent holes

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Publication number Priority date Publication date Assignee Title
US3716869A (en) * 1970-12-02 1973-02-13 Nasa Millimeter wave antenna system
US3982215A (en) * 1973-03-08 1976-09-21 Rca Corporation Metal plated body composed of graphite fibre epoxy composite
JPS5974704A (en) * 1982-10-22 1984-04-27 Hitachi Ltd Waveguide
US5198828A (en) * 1991-08-29 1993-03-30 Rockwell International Corporation Microwave radar antenna and method of manufacture
US5761053A (en) * 1996-05-08 1998-06-02 W. L. Gore & Associates, Inc. Faraday cage
US5739734A (en) * 1997-01-13 1998-04-14 Victory Industrial Corporation Evanescent mode band reject filters and related methods
US6181220B1 (en) 1999-04-19 2001-01-30 Lucent Technologies, Inc. Method for reducing electrical discharge in a microwave circuit, and a microwave circuit treated by the method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60246104A (en) * 1984-05-22 1985-12-05 Showa Denko Kk Cylindrical radio wave reflecting tube
EP0210543B1 (en) * 1985-08-02 1994-03-02 Texas Instruments Incorporated Radar rotary joint
US6265703B1 (en) * 2000-06-02 2001-07-24 The Ferrite Company, Inc. Arc suppression in waveguide using vent holes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 0101, no. 08 (E - 398) 23 April 1986 (1986-04-23) *

Also Published As

Publication number Publication date
DE602004016824D1 (en) 2008-11-13
EP1597792B1 (en) 2008-10-01
KR100680082B1 (en) 2007-02-08
NO20054146D0 (en) 2005-09-06
KR20050102673A (en) 2005-10-26
US20040164823A1 (en) 2004-08-26
EP1597792A1 (en) 2005-11-23
NO20054146L (en) 2005-11-23
US6927654B2 (en) 2005-08-09

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