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Publication numberUS3725719 A
Publication typeGrant
Publication dateApr 3, 1973
Filing dateNov 30, 1970
Priority dateNov 30, 1970
Also published asDE2157573A1
Publication numberUS 3725719 A, US 3725719A, US-A-3725719, US3725719 A, US3725719A
InventorsM Seldon, L Garbini
Original AssigneeVarian Associates
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and aritcle for inhibiting gaseous permeation and corrosion of material
US 3725719 A
Abstract
A method and apparatus for inhibiting gaseous permeation and corrosion of materials is disclosed. Gaseous permeation and corrosion of materials is inhibited by the provision of a coating of gold and tantalum over the surface of the article to be protected. In a preferred method of applying the coating, the gold and tantalum are co-deposited by sputtering to form the coating. The gold and tantalum coating is preferably protected by an organic coating to form a barrier to prevent contact of the gold and tantalum coating with corrosion-producing materials. The gold and tantalum coating reduces hydrogen permeation of coated materials by factors of several thousand compared to a reduction factor of approximately five times for a pure gold coating of comparable thickness.
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United States Patent Seldon et al.

METHOD AND ARITCLE FOR INHIBITING GASEOUS PERMEATION AND CORROSION OF MATERIAL Inventors: Martin M. Seld0n; Leo J. Garbini, both of Sunnyvale, Calif.

Assignee: Varian Associates, Palo Alto, Calif.

Filed: Nov. 30, 1970 Appl. No.: 93,902

References Cited UNITED STATES PATENTS Knippenberg et al. ..75/165 Spence ...29/183.5 Laegreid et al ..204/l92 Apr. 3, 1973 .Att0rneyStanley Z. Cole and Vincent W. Cleary [57] ABSTRACT A method and apparatus for inhibiting gaseous permeation and corrosion of materials is disclosed. Gaseous permeation and corrosion of materials is inhibited by the provision of a coating of gold and tantalum over the surface of the article to be protected. in a preferred method of applying the coating, the gold and tantalum are co-deposited by sputtering to form the coating. The gold and tantalum coating is preferably protected by an organic coating to form a barrier to prevent contact of the gold and tantalum coating with corrosion-producing materials. The gold and tantalum coating reduces hydrogen permeation of coated materials by factors of several thousand compared to a reduction factor of approximately five times for a pure gold coating of comparable thickness.

5 Claims, No Drawings METHOD AND ARITCLE FOR INHIBITING GASEOUS PERMEATION AND CORROSION OF MATERIAL GOVERNMENT CONTRACT The invention herein described was made in the course of or under a contract with the US. Air Force.

DESCRIPTION OF THE PRIOR ART Heretofore, articles and devices have been coated with gold to reduce permeation of the coated article or device by hydrogen. Samples of prior art patents directed to use of a gold coating are: US. Pat. No. 3,239,300 issued Mar. 8, 1966 and US. Pat. No. 3,284,175 issued Nov. 8, l966. The former patent is directed to a gold coating on the metallic envelope portion of an electron tube, whereas the second patent is directed to a gold coating on high strength steel articles to prevent embrittlement and weakening of the steel article by hydrogen permeation. It has been found that a gold coating reduces hydrogen permeation of the underlying material by a factor of approximately five. It is desirable to obtain an improved coating which greatly reduces the gaseous permeation of the coated member by factors greatly in excess of five.

SUMMARY OF THE PRESENTINVENTION The principal object of the present invention is the provision of improved method and apparatus for inhibiting gaseous permeation and corrosion of materials.

One feature of the present invention is the provision of a gaseous-permeation inhibiting coating consisting of gold and tantalum. I

In another feature of the present invention, a gold and tantalum coating for inhibiting gaseous permeation of an underlying article is protected by an overlaying coating of organic resin selected from the class consisting of fluorocarbon resin, silicone resin, epoxy resin, silicone-alkyd co-resins, and epoxy co-resins with phenolic, urea or melamine.

In another feature of the present invention, the material which forms the gaseous permeation-inhibiting coating is applied by co-deposition of gold and tantalum.

In another feature of the present invention, the gold and tantalum gaseous-permeation-inhibiting layer is formed by co-sputtering gold and tantalum onto the article.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been discovered that a coating of gold and tantalum over a material greatly inhibits permeation of the coated surface by gases, such as hydrogen. For example, a cold rolled steel membrane which is 0.002 inch thick and coated with a layer of co-sputtered gold and tantalum to a thickness of approximately 3 microns with an overlaying protecting coating of silicone resin reduces hydrogen permeation of the membrane by a factor of several thousand as compared with a reduction of only six times for a silicone resin coated membrane and a reduction of only five times for a gold coated membrane.

7 cent, for improved performance. The cold rolled steel membrane which was coated was analyzed and found to contain constituents other than iron in the following parts per million: carbon, 800 parts per million; manganese, 400 parts per million; nickel, 170 parts per million; chromium, 80 parts per million; and copper, 40 parts per million. The permeation tests were conducted at 100C with hydrogen gas supplied to the surface of the membrane at approximately 1 atmosphere pressure. A vacuum was pulled on the opposite side of the membrane. The coated membrane was baked in vacuum at 400C for 18 hours prior to the gas permeation test.

It is believed that the manganese and iron diffused to the surface of the membrane through the gold and tantalum coating during the baking process. A black coating was found on the high vacuum side of the membrane and it is believed that this occured due to diffusion of the manganese out of the iron membrane. The manganese coating had no effect on hydrogen permeation.

It is believed that the greatly reduced gaseous permeation rates through the gold and tantalum coating is due to the fact that the gold provides a smooth and continuous coating that tends to fill in surface discontinuities in the material being coated and that hydrogen is actively absorbed by the tantalum in the coating and results in hydrogen being held on the surface of the coating in some relatively stable form, such as one of the tantalum hydrides or other stable compounds. The silicone resin overcoat serves to inhibit exposure of the gold and tantalum coating to moisture or other corrosion-producing materials.

The gold and tantalum coating is preferably formed by co-sputtering tantalum and gold onto the surface of the article to be protected. A particularly useful apparatus for sputtering gold and tantalum onto the material to be coated is low energy sputtering equipment manufactured by Consolidated Vacuum Corporation in which three elements are employed for sputtering in a plasma discharge generally formed in an inert gas such as argon, krypton, or Xenon at a reduced pressure, as of l X 10' torr. Such an apparatus is described in an article titled, Some Practical Considerations In The Use Of Low Energy Sputtering appearing in the Dec., 1965 issue of SCP and Solid State Technology, pages 30-33.

The gold and tantalum coating is preferably protected by an organic coating selected from the group consisting of fluorocarbon resins, silicone resins, epoxy resins, silicone-alkyd co-resins, and epoxy co-resins with phenolic, urea or melamine. A particularly suitable organic protective material comprises silicone resin marketed under the name Vac-Seal by Space Environment Laboratories of Boulder, Colorado, such material being available in spray can form for spraying the protective silicone coating onto the gold and tantalum layer.

Silicone resins are well-known for their ability to repel water and to resist heat. Many of these resins will withstand temperatures in excess of 500F. The following pure silicone resins may be utilized for the protective coating over the gold and tantalum layer: Dow- Corning, 804, 805, 806 A, 808, and 847; General Electric SRlll, SR112, SR53, SR82, SR119, SR124 and SR125; and Union Carbides Ucarsil 104. For thin films (less than 1 mil), SR53 and Ucarsil104 are preferred. For thicker films (1-3 mils) DC 808, GE SRll 1, SR112, SR119, and SR125 are preferred.

There are many epoxy resins available with not too widely different properties. They are better than silicone resins in hardness and corrosion resistance, but are not as good in heat resistance and moisture resistance. A typical epoxy resin is Shell Epon 1001.

The gaseous-permeation-inhibiting gold and tantalum coating with the protective organic coating is particularly useful for coating of vacuum enclosures of electron tubes, such as klystrons, traveling wave tubes, magnetrons and the like. These coatings prevent hydrogen gas from permeating the envelope and producing a number of free gas ions within the evacuated device. The coating is also useful on space vehicles, cryogenic and undersea pressure vessels, and vehicle wall constructions as well as in special structural steel applications.

The coatings of the present invention are also applicable to other devices for protection against corrosion. When the gold and tantalum coating is used in conjunction with a coating of organic resin, such as silicone resin, the formation of corrosion products is inhibited. Corrosion products or products formed by gas and ion collisions at the surface of the coated article are prevented from passing through the material by the coating. Under typical atmospheric conditions, ion and gas collisions at the surface of an object result in dissociation of the gases which are present. One of the results of this surface activity is the generation of atomic hydrogen that freely enters the surface layers of the object and then moves through the material. Dependent upon the condition of the material, hydrogen, in the atomic state, can recombine at the inside surface in a variety of manners to generate deleterious compounds, such as molecular hydrogen, methane, water, etc. Other compounds which are not products of hydrogen reaction, but of substitution reaction, include carbon monoxide and carbon dioxide. Use of the coatings of the present invention inhibit these phenomena to a considerable degree.

Permeation of hydrogen into metals can have a variety of undesirable effects on the characteristics of the metal. Such undesired characteristics include embrittlement and weakening of the metal such as those discussed in the aforecited US. Pat. No. 3,284,175.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. In a method for inhibiting hydrogen permeation of the surface of an article, the steps of:

simultaneously sputtering gold and tantalum particles onto said surface to form a gold and tantalum coating on said surface, and

heating the coating at about 400 C for about 18 hours.

2. The method of claim 1 in which said gold and tantalum coating is about 3 microns thick.

3. An article having an outer surface which is resistant to hydrogen permeation, comprising:

a first member having a selected surface area, and

a gold and tantalum coating on said selected surface area to form said outer surface of said article, said coating being formed by the steps of:

simultaneously sputtering gold and tantalum particles onto said surface area to form said gold and tantalum coating on said surface area, and

heating the coating at about 400 C for about 18 hours.

4. The article of claim 3 in which said gold and tantalum coating is about 3 microns thick.

5. An electron tube comprising an anode; a cathode; evacuated envelope means for enclosing said anode and cathode, said envelope means having a selected surface area; and a gold and tantalum coating on said surface area for inhibiting hydrogen permeation of said evacuated enclosure, said gold and tantalum coating being formed by the steps of:

simultaneously sputtering gold and tantalum particles onto said surface area to form said gold and tantalum coating on said surface area, and

heating the coating at about 400 C for about 18 hours.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3196536 *Jul 23, 1962Jul 27, 1965Philips CorpMethod of connecting graphite articles to one another or to articles of different materials
US3284175 *Mar 9, 1964Nov 8, 1966Neville S SpenceGold coated steel article
US3324019 *Dec 11, 1962Jun 6, 1967Schjeldahl Co G TMethod of sputtering sequentially from a plurality of cathodes
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4486622 *Jul 1, 1983Dec 4, 1984Siemens AktiengesellschaftCase for a semiconductor component
US5493320 *Sep 26, 1994Feb 20, 1996Lexmark International, Inc.Ink jet printing nozzle array bonded to a polymer ink barrier layer
US20150349226 *May 28, 2015Dec 3, 2015Toyoda Gosei Co., Ltd.Light-emitting element and method of manufacturing the same
EP0785073A3 *Jan 9, 1997Nov 11, 1998Lexmark International, Inc.Coated nozzle plate for ink jet printing
Classifications
U.S. Classification313/317, 428/553, 204/192.15, 428/672, 428/926
International ClassificationC23C30/00
Cooperative ClassificationY10S428/926, C23C30/00
European ClassificationC23C30/00