Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming multiple superposed electrolytic coatings
Reexamination Certificate
1997-10-03
2001-04-17
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming multiple superposed electrolytic coatings
C205S191000, C205S203000, C205S229000, C148S276000
Reexamination Certificate
active
06217737
ABSTRACT:
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 by themselves are typically effective for sealing out corrosives, but are subject to scratching; and nicking resulting in rapid corrosion; and
6. Connector shells formed of corrosion-resistant steel are excessively expensive to produce 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
C
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 of 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. In yet another alternative, the plating can include cadmium.
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 of at least approximately 0.00002 inch 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 cadmium.
REFERENCES:
patent: 3683331 (1972-08-01), Overholser
patent: 4225399 (1980-09-01), Tomita
patent: 4239838 (1980-12-01), Miller et al.
patent: 4490184 (1984-12-01), Forcht et al.
patent: 4968389 (1990-11-01), Satoh et al.
patent: 5232891 (1993-08-01), Hormann et al.
patent: 9103583 (1991-03-01), None
International Search Report; Dec. 12, 1998; 4 p.
HiRel Connectors Inc.
Sheldon & Mak
Wong Edna
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