CORROSION-RESISTANT CONDUCTIVE CONNECTOR SHELL

Abstract: A corrosion-resistant and electrically conductive connector shell (10) includes a shell member (11) formed of an aluminum alloy; an anodic surface coating (14) formed on and extending into the shell member, having an approximate thickness between 0.0008 inch and 0.0018 inch; and a conductive metal plating (16) covering and sealing the anodic surface coating. The metal plating can be a single layer of high purity aluminum having a thickness of 0.0002 inch. Alternatively, the metal plating can include a layer (18) of a first metal such as high purity aluminum on the anodic surface coating and having a thickness (approximately 0.00002 inch) being sufficient for forming a conductive plating platform, and a layer (20) of a second metal such as nickel or an alloy of zinc and nickel having a thickness of approximately 0.001 inch on the layer of first metal. Also disclosed is a method for forming a corrosion-resistant and electrically conductive connector shell including the steps of providing an aluminum alloy shell member; forming an anodic coating on and extending into the shell member; and plating a layer of aluminum by ion vapor deposition on the anodic coating.

Description: CORROSION-RESISTANT CONDUCTIVE CONNECTOR SHELL BACKGROUND The present invention relates to electrical connectors, and more particularly to connectors for use in corrosive environments such as are found near oceans and the like. Electrical connectors are widely used in aircraft and other vehicles that are required to be exposed to corrosive contamination by salt spray, for example. While being otherwise desirable for low cost and light weight, connectors having aluminum outer shells have been generally rejected in high- performance applications because of rapid corrosion under exposure to salt spray environments. Conventional surface treatments have proven unsatisfactory for a number of reasons. For example: 1. Ordinary anodic coatings are easily scratched through, corrosion proceeding rapidly from even very small lesions; 2. Hard anodic coatings by themselves are porous, being ineffective for excluding corrosives; 3. All anodic coatings are non-conductive, whereas electrical conductivity is usually required; 4. Conventional paint is also non-conductive and easily scratched, and conductive paint affords less corrosion resistance than conventional paint; 5. Plated coatings are typically ineffective for sealing out corrosives, being porous, subject to peeling, or subject to scratching; 6. Connector shells formed of corrosion-resistant steel are excessively expensive to provide and undesirably heavy; and substitution of titanium is even more expensive, being also fifty percent heavier than aluminum. Thus there is a need for a lightweight corrosion- resistant conductive connector shell that overcomes the disadvantages of the prior art. SUMMARY The present invention meets this need by providing an aluminum shell having a combination of anodic and plated coatings. In one aspect of the invention, a corrosion-resistant and electrically conductive connector shell includes a shell member formed of an aluminum alloy; an anodic surface coating formed on and extending into the shell member, the anodic surface coating having a hardness of not less than R c 60; and a conductive coating covering and sealing the anodic surface coating. The term "shell" is inclusive of components thereof such as coupling ring, backshell, etc. The anodic surface coating can have a thickness being between approximately 0.0008 inch and approximately 0.0018 inch. The hardness of the anodic surface coating can be approximately R 72. The conductive coating preferably includes metallic plating for high conductivity. Preferred plating is a layer of ion vapor deposited high purity aluminum and having a thickness effective for sealing the anodic coating. The layer of high purity aluminum can have a thickness of at least approximately 0.0002 inch. Alternatively, the metallic plating can include a layer including zinc, nickel or cadmium that preferably has a thickness of at least approximately 0.0002 inch for durability and wear resistance. In a further alternative, the metallic plating can include a layer of a first metal on the anodic surface coating, and a layer of a second metal on the layer of first metal . The layer of first metal can have a thickness of at least approximately 0.00002 inch being effective for bonding the layer of second metal. Preferably the layer of first metal is high purity ion vapor deposited aluminum having a thickness sufficient for providing a conductive plating platform, the layer of second metal including nickel and having a thickness of at least approximately 0.0002 inch. The layer of second metal can include an alloy of zinc and nickel. In yet anther alternative, the plating can include zinc, nickel or cadmium. The metallic plating can include an alloy of zinc and nickel. The connector shell can be part of a connector assembly in combination with an insulative carrier supported by the connector shell, and at least one electrical contact extending within the carrier in electrical isolation from the shell. In another aspect of the invention, a method for forming a corrosion-resistant and electrically conductive connector shell includes the steps of: (a) providing an aluminum alloy shell member; (b) forming an anodic coating on and extending into the shell member; and (c) plating a sealed conductive coating on the anodic coating. The forming step can include extending the anodic coating to a depth of at least approximately 0.0008 inch at a hardness of at least R c 60. Preferably the plating step can include ion vapor deposition of high purity aluminum to a thickness effective for sealing the anodic coating. The plating step can further include extending the high purity aluminum to a thickness of at least approximately 0.0002 inch. Alternatively, the plating step can include plating a layer of a first metal on the anodic coating, and sealingly plating a layer of a second metal on the layer of first metal. The plating step can include extending the layer of first metal to a thickness sufficient for providing a conductive plating platform, and extending the layer of second metal to a thickness of at least approximately 0.0002 inch for providing a desired combination of resistance to wear and corrosion, the second metal being selected from the group consisting of nickel and an alloy of zinc and nickel . DRAWINGS These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings , where : Figure 1 is a side view of an electrical connector including a connector shell according to the present invention; Figure 2 is a side sectional detail view of a surface portion of the connector shell of Fig. 1; and Figure 3 is a flow diagram of a process for forming the connector shell of Fig. 1. DESCRIPTION The present invention is directed to an electrical connector shell that is particularly effective in harsh environments. With reference to Figs. 1 and 2 of the drawings, a connector assembly 10 includes a connector shell 11 that is made from a base member 12 having an anodic coating 14 and a conductive coating 16 having a thickness C. The coating 16 can include a first plated layer 18 and a second plated layer 20. In one preferred alternative that is further described below, the conductive coating 16 can have just one layer being a sacrificial anode of ion-vapor-deposited (IVD) high purity aluminum. The base member 12 is formed of a suitable aluminum alloy for providing a desired combination of light weight and high strength. The anodic coating 14 transforms a portion of the base member 12 at the surface thereof to a non-conductive material, the coating 14 extending slightly below the surface and also slightly enlarging the base member 12. In other words, the anodic coating 14 has a thickness A, a portion B of which extends below the original surface of the base member 12. Preferably, the anodic coating 14 is formed by a process that is commercially known as "hard anodizing" or "Type III anodizing" which produces a surface hardness of not less than R 60 and typically R 72, wherein the term "Rc" means the Rockwell C Scale as is commonly known. Determinations of Rockwell hardness are normally made by equipment that makes an impression using a small diameter hardened ball at a predetermined loading, hardness readings being correlated to the depth of the impression. In contrast to conventional anodizing in which the thickness A is approximately 0.0002 inch, the thickness A using the preferred hard anodizing is between approximately 0.0008 inch and approximately 0.0018 inch, being typically approximately 0.0015 inch. In commercial processes of hard anodizing, there typically is a supplemental treatment of immersion in heated water, dilute nitric acid, or a dichromate solution, the dichromate treatment having the effect of closing pores of the anodic coating. It will be understood that contrasting hardness measurements as between conventional or "type II" anodizing and hard anodizing are in part due to differences in SUBSTITUTE SHEET (RULE G rH X! 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Claims: CLAIMS 1. A corrosion-resistant and electrically conductive connector shell comprising: (a) a shell member formed of an aluminum alloy; (b) an anodic surface coating formed on and extending into the shell member, the anodic surface coating having a hardness of not less than R c 60; and (c) a conductive coating covering and sealing the anodic surface coating. 2. The connector shell of claim 1, wherein the anodic surface coating has a thickness being between approximately 0.0008 inch and approximately 0.0018 inch. 3. The connector shell of claim 1, wherein the hardness of the anodic surface coating is approximately R c 72. 4. The connector shell of claim 1, wherein the conductive coating comprises metallic plating. 5. The connector shell of claim 4, wherein the metallic plating comprises a layer of ion vapor deposited high purity aluminum to a thickness effective for sealing the anodic coating. 6. The connector shell of claim 5, wherein the layer of high purity aluminum has a thickness of at least approximately 0.0002 inch. 7. The connector shell of claim 4, wherein the metallic plating comprises a layer of at least one material selected from the group consisting of zinc, nickel and cadmium. 8. The connector shell of claim 7, wherein the layer of the at least one material has a thickness of at least approximately 0.0002 inch. 9. The connector shell of claim 4, wherein the metallic plating comprises a layer of a first metal on the anodic surface coating, and a layer of a second metal on the layer of first metal. 10. The connector shell of claim 9, wherein the layer of first metal has a thickness of at least approximately 0.00002 inch. 11. The connector shell of claim 9, wherein the layer of first metal is high purity ion vapor deposited aluminum having a thickness sufficient for providing a conductive plating platform, and the layer of second metal comprises nickel, the second layer having a thickness of at least approximately 0.0002 inch. 12. The connector shell of claim 11, wherein the layer of second metal comprises an alloy of zinc and nickel. 13. The connector shell of claim 4, wherein the metallic plating comprises at least one material selected from the group consisting of zinc, nickel and cadmium. 14. The connector shell of claim 13, wherein the metallic plating comprises an alloy of zinc and nickel. 15. A connector assembly comprising the connector shell of claim 1 in combination with an insulative carrier supported by the connector shell, and at least one electrical contact extending within the carrier in electrical isolation from the shell. 16. A corrosion-resistant and electrically conductive connector shell comprising: (a) a shell member formed of an aluminum alloy; (b) an anodic surface coating formed on and extending into the shell member, the anodic surface coating having a hardness of approximately R c 72, and a thickness being between approximately 0.0008 inch and approximately 0.0018 inch; and (c) a conductive metal plating covering and sealing the anodic surface coating, the metal plating comprising: (d) a first layer of ion vapor deposited high purity aluminum having a thickness effective for providing a conductive plating platform, and a second layer comprising a material selected from the group consisting of nickel and an alloy of zinc and nickel, the second layer having a thickness of not less than approximately 0.0002 inch. 17. A method for forming a corrosion-resistant and electrically conductive connector shell, comprising the steps of: (a) providing an aluminum alloy shell member; (b) forming an anodic coating on and extending into the shell member; and (c) plating a sealed conductive coating on the anodic coating. 18. The method of claim 17, wherein the forming step comprises extending the anodic coating to a depth of at least approximately 0.0008 inch at a hardness of at least R c 60. 19. The method of claim 18, wherein the forming step further comprises a supplemental dichromate treatment. 20. The method of claim 17, wherein the plating step comprises ion vapor deposition of high purity aluminum to a thickness effective for sealing the anodic coating. 21. The method of claim 20, wherein the plating step further comprises extending the high purity aluminum to a thickness of at least approximately 0.0002 inch. 22. The method of claim 17, wherein the plating step comprises : (a) plating a layer of a first metal on the anodic coating; and (b) sealingly plating a layer of a second metal on the layer of first metal. 23. The method of claim 22, wherein the plating step comprises extending the layer of first metal to a thickness sufficient for providing a conductive plating platform, and extending the layer of second metal to a thickness of at least approximately 0.0002 inch, the second metal being selected from the group consisting of nickel and an alloy of zinc and nickel.

Inventors: BAUMANN FREDERICK B B, BAUMANN, FREDERICK, B., B.
Applicants: BAUMANN FREDERICK B B, HIREL CONNECTORS INC, BAUMANN, FREDERICK, B., B., HIREL CONNECTORS INC.
Application year: 1998
Main classification: H01R13
IPC codes: C25D11, H01R13