Cathodic debonding prevention method and apparatus

Abstract

A method for improving service life in a connector for joining to a cathodically protected platform includes providing a metallic connector for joining to a cable. A non-conductive coating is provided on the connector proximate the cable. A hydroxide ion diffusion distance is determined that will insure dilution of hydroxide ions to a level that will prevent damage to an encapsulant and non-conductive coating bond on the connector. A polymer encapsulant is molded around the non-conductive coating and the cable to seal the assembled cable in the connector such that the encapsulant and non-conductive coating bond is formed at a greater path distance than the determined hydroxide ion diffusion distance from any hydroxide ion source.

Claims

1. A method for improving service life in a connector for joining to a cathodically protected platform comprising the steps of: providing a cable; providing a metallic connector having a non-conductive coating on a portion thereof wherein exposed cathodically protected portions of the metallic connector are hydroxide ion sources; assembling the cable in the metallic connector; determining a hydroxide ion diffusion distance away from the exposed cathodically protected portions of the metallic connector as the distance that will dilute hydroxide ions for reducing cathodic delamination; and molding a polymer encapsulant around the cable and the non-conductive coating on the metallic connector forming a polymer encapsulant and non-conductive coating bond therebetween to seal the assembled cable in the metallic connector such that the polymer encapsulant and non-conductive coating bond is formed at a greater distance than the determined hydroxide ion diffusion distance from exposed cathodically protected portions of the metallic connector; wherein the step of providing a metallic connector having a non-conductive coating further comprises providing a raised region around the metallic connector underneath the non-conductive coating proximate exposed cathodically protected portions of the metallic connector such that the raised region in combination with the non-conductive coating and the distance between the exposed cathodically protected portions of the metallic connector and the polymer encapsulant and non-conductive coating bond is at least the determined hydroxide ion diffusion distance.

2. A method for improving service life in a connector for joining to a cathodically protected platform comprising the steps of: providing a cable; providing a metallic connector having a non-conductive coating on a portion thereof wherein exposed cathodically protected portions of the metallic connector are hydroxide ion sources; providing a non-conductive ring around the metallic connector and the non-conductive coating and sealed there against between exposed cathodically protected portions of the metallic connector and the encapsulant mounting portion; assembling the cable in the metallic connector; determining a hydroxide ion diffusion distance away from the exposed cathodically protected portions of the metallic connector as the distance that will dilute hydroxide ions for reducing cathodic delamination; and molding a polymer encapsulant around the cable and the non-conductive coating on the metallic connector forming a polymer encapsulant and non-conductive coating bond therebetween to seal the assembled cable in the metallic connector such that the polymer encapsulant and non-conductive coating bond is formed at a greater distance than the determined hydroxide ion diffusion distance from exposed cathodically protected portions of the metallic connector.

3. The method of claim 2 wherein the non-conductive zing is provided on the non-conductive coating by heat shrink fitting.

4. The method of claim 2 wherein the non-conductive ring is made from an elastomeric material, and the non-conductive ring is provided on the non-conductive coating by elastically expanding the ring and allowing the ring to contract around the non-conductive coating.

5. The method of claim 2 wherein the determined hydroxide ion diffusion distance is at least about 0.5 inches.

6. A delamination resistant marine connector for joining an existing cable to a cathodically protected outlet comprising: a metallic connector body having a terminal portion connecting to the cathodically protected outlet and a back shell portion capable of receiving the existing cable therein; a non-conductive coating disposed on said metallic connector body back shell portion, other metallic portions of said metallic connector body remaining exposed; and an encapsulant molded around said non-conductive coating and the existing cable and bonded thereto such that said encapsulant is molded a distance from the other metallic portions of said metallic connector body remaining exposed to prevent concentrated hydroxide ions from eroding the bonded region between said encapsulant and said non-conductive coating; wherein said metallic connector body back shell portion has a flange formed there around and coated by said non-conductive coating, the flange being provided to increase the distance between said encapsulant and the other metallic portions of said metallic connector body remaining exposed.

7. The apparatus of claim 6 wherein said encapsulant is molded around said non-conductive coating and said metallic connector body back shell portion at least 0.5 inches from the other metallic portions of staid metallic connector body remaining exposed.

8. A delamination resistant marine connector for joining an existing cable to a cathodically protected outlet comprising: a metallic connector body having a terminal portion connecting to the cathodically protected outlet and a back shell portion capable of receiving the existing cable therein; a non-conductive coating disposed on said metallic connector body back shell portion, other metallic portions of said metallic connector body remaining exposed; an anti-diffusion collar made from a non-conductive material and sealed against said non-conductive coating on said metallic connector body back shell portion between said encapsulant and the other metallic portions of said metallic connector body remaining exposed; and an encapsulant molded around said non-conductive coating and the existing cable and bonded thereto such that said encapsulant is molded a distance from the other metallic portions of said metallic connector body remaining exposed to prevent concentrated hydroxide ions from eroding the bonded region between said encapsulant and said non-conductive coating.

9. The apparatus of claim 8 wherein said encapsulant is molded around said non-conductive coating and said metallic connector body back shell portion at least 0.5 inches from the other metallic portions of said metallic connector body remaining exposed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Reference is made to the accompanying drawings in which are shown an illustrative embodiment of the invention, wherein corresponding reference characters indicate corresponding parts, and wherein:

(2) FIG. 1 is a diagram showing a prior art connector subject to cathodic debonding;

(3) FIG. 2 is a diagram showing a first embodiment of a connector protected against cathodic debonding;

(4) FIG. 3 is a diagram showing a second embodiment of a connector protected against cathodic debonding; and

(5) FIG. 4 is a diagram showing a third embodiment of a connector protected against cathodic debonding.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 2 suggests a method by which cathodic debonding can be stopped. If the flow of M.sup.+ charge balance cations to the site of active debonding is disrupted, the cathodic debonding process slows or completely stops. This is easier than trying to stop the movement of the oxygen (O.sub.2) and water (H.sub.2O) needed for the cathodic delamination reaction to occur. Because oxygen and water are either uncharged or possess a small dipole, they can diffuse through polymers, whereas M.sup.+ cations, being charged, cannot.

(7) FIG. 2 shows a first embodiment of a connector 10 for avoiding or reducing cathodic debonding. As above, connector 10 is joined to a cable 12 having multiple elements 14. Connector 10 has a connector body 16 that includes a back shell portion 18 and a terminal connection portion 20. Back shell portion 18 is covered by a non-conductive coating 22. Connector 10 at its terminal connection portion 20 is joined to an outlet 24 that may be on a vessel 26 or other structure. As before, connector 10 is affixed in outlet 24 by a mounting ring 28. An encapsulant 30 is applied to the exterior of non-conductive coating 22. The vessel 26 is protected from corrosion by cathodic protection system 32.

(8) In this embodiment, encapsulant bond-line/interface 34 is moved away from mounting ring 28 and plug 24 interface by a distance d. Distance d is a diffusion path length away from a hydroxide ion generating structure (in this case locking ring 28) that allows sufficient diffusion of ions to resist debonding. Diffusion path length d is dependent on the hydroxide ions present in the environment and the turbulence in the environment. Greater turbulence results in greater mixing and a lower hydroxide ion concentration at a given distance. Distances of 0.01 inches have been shown to be insufficient to protect from debonding. Diffusion distances of 0.5 inches have found to provide sufficient diffusion to protect encapsulant 30 from debonding. The minimum distance d can be established by experimental testing. Once further data is collected modeling can also be used to calculate a distance d that will give the necessary connector life given a particular connector design.

(9) FIG. 3 shows another embodiment. Diffusion distance d does not need to be in a straight line from a hydroxide ion source. In this embodiment, connector 10 includes a flange 36 positioned around back shell portion 18. Flange 36 is covered with a non-conductive coating 22 so that it will not be a hydroxide ion source. For hydroxide ions to reach bond-line/interface 34, they must travel from the locking ring 28, across the top of flange 36, and radially inward to interface 34. The region across the top of flange 36 is expected to have greater turbulence thereby subjecting hydroxide ions to dilution and lowering the pH at interface 34.

(10) FIG. 4 shows another embodiment, further illustrating apparatus for utilizing the teachings herein. Connector 10 features an anti-diffusion collar 38 positioned between locking ring 28 and interface 34. Anti-diffusion collar 38 can be a non-conductive member that is sealed against the non-conductive coating 22 around back shell portion 18. Anti-diffusion collar 38 can be made from an elastomeric material that is positioned around back shell portion 18 prior to the assembly of connector 10 to cable 12. Anti-diffusion collar 38 can be heat shrunk to seal against back-shell portion 18 or can be stretched over back shell portion 18. Encapsulant 30 can be molded around back shell portion 18 and cable 12 after positioning of the anti-diffusion collar 38 and assembly of the cable 12 in connector 10. In operation, anti-diffusion collar 38 will extend radially outward away from interface 34 to provide the distance d. It is expected that this will reduce the concentration of hydroxide ions that are communicated from cathodically protected components to interface 34.

(11) It will be understood that these teachings can be applied to many different types of connectors and the descriptions herein are merely for illustrative purposes. There may be many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

(12) The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description only. It is not intended to be exhaustive, nor to limit the invention to the precise form disclosed; and obviously, many modification and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.