US 3853730 A
A marine cathodic protection device for aluminum hulls, stern drives and outboard motors, adapted for through hull installation on the bottom of a boat. Housings utilizing airfoil cross-section reduce drag and afford protection for the electrode surfaces.
Claims available in
Description (OCR text may contain errors)
United States Patent Anderson Dec. 10, 1974  REFERENCE ELECTRODE 2,934,484 4/1960 Anderson 204/196 3,272,731 9/1966 Hutchison et al 204/196  Inventor: m Anders, Fond du 3,278,408 10/1966 Leonard et a1. 204/195 P 3,445,369 5/1969 Porter et al. 204/195 P  Assigneez Brunswick Corporation Skokie In. 3,625,851 12/1971 Geld 204/195 F  Filed: Mar. 29, 1973 primary E T  APP] 345,869 Attorney, Agent, or FirmWil1iarn G. Lawler, Jr.
52 US. Cl 204/195 F, 204/196  ABSTRACT 51 Int. Cl. G01n 27/30, C23f 13/00 A marine cathodic Protection device for n m  Field of Search 204/147, 196, 195 F, 195 P hulls, stern drives and outboard motors, adapted for through hull installation on the bottom of a boat.  Refe e e Ci d Housings utilizing airfoil cross-section reduce drag and UNITED STATES PATENTS afford protection for the electrode surfaces.
2,910,420 10/1959 Preiser 204/196 3 Claims, 6 Drawing Figures 5 PATENTEQ 352 I 01974 snmlor z REFERENCE ELECTRODE BACKGROUND OF THE INVENTION With the advent of aluminum hulled boats, aluminum stern drive propulsion units, and larger outboards with sizable areas of aluminum casing below the water, it has become increasingly important to provide adequate cathodic protection; particularly in salt, brackish or polluted waters. In addition, visits to crowded marinas where shore power is often taken aboard makes cathodic protection a virtual necessity.
The basic concept of cathodic protection of vessels is not new, and various configurations of anodes and reference electrodes have been tried. For example, U.S. Pat. No. 3,117,070 to the inventor teaches a bronze half-cell suitable for use on a steel hull, and the assignee hereof has marketed a cathodic protection device employing cylindrical electrodes mounted through the transom of the boat.
One problem with the prior art devices which mounted through the transom was that they were out of the water when the boat was running at high speed. This resulted in significant loss of protection.
Another problem with prior art electrodes which were capable of being mounted on the bottom of a boat was the wearing away of the active material on the anode with a resulting deterioration in the effectiveness of the system.
Accordingly it is an objective of the invention to provide an anode and a reference electrode particularly suited for installation on the bottom of a boat.
It is a further objective of the invention to protect the anode and reference electrode from abrasive damage such as that encountered when a boat runs aground.
It is a still further objective of the invention to maximize the ruggedness and reliability of the aforesaid electrodes by enclosing them within rugged corrosion and erosion resistant housings.
Another objective of the invention, consistent with the foregoing, is to reduce water drag on the electrodes through utilization of streamlined housings.
SUMMARY OF THE PRESENT INVENTION Basically the invention comprises a reference electrode and a companion anode, each retained by a separate mounted housing of modified airfoil cross-section. The anode s platinum electrode surface is exposed only abaft the point of maximum camber of its housing, and the reference electrode is enclosed within a chamber opening to the surrounding water through a series of apertures. Means for mounting the housings upon the bottom of the boat are provided, including conduits to permit electrical connection of the anode and reference electrode to a control circuit.
Chief among the advantages of the invention is protection of the electrodes while affording them maximum possible exposure to the surrounding seawater, and at a minimum cost in drag. A further advantage of the invention is increased protective capacity of electrodes through selective use of materials, again made possible by the configuration of the aforementioned housings. Lastly, the invention provides rugged and reliable electrodes at a cost consistent with their use on small pleasure crafts.
Other objectives, advantages, and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1a and lb are perspective views of an anode and reference electrode respectively of the invention.
FIGS. 2a and 2b are longitudinal cross-sectional views of an anode and a reference electrode respectively of the invention.
FIGS. 3a and 3b are lateral cross-sectional views of the anode and reference electrode of FIG. 1 taken respectively along lines 3a3a and 3b3b.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the similarities and the differences between an anode 1 of the invention and a reference electrode 2. The overall size and shape of the housings 3 and 4 of the two units are substantially identical. The housings have been given a modified airfoil shape so that they offer minimum resistance to passage through the water in the direction of the arrows in FIG. 1. To avoid erosion and corrosion the housings are preferably made of an acetal polymer plastic such as Celenex. This material was selected for its resistance to the environment created by the electrolytic action at the electrodes.
The anode electrode 5 extends aft from a point slightly aft of the maximum height or camber of the anode housing 3, to a point just forward of the trailing edge of the housing 3; so that it is protected from direct frontal contact with the fluid stream passing over the anode, and with sand or other solid objects over which may come in contact with the bottom of the boat and the forward part of the housing.
As illustrated best in FIGS. la and 3a, the edges of the anode housing 3 surrounding the anode electrode 5 are rounded so that they contact the surface of that electrode at an oblique angle. This affords the anode maximum effective contact with the water, while still permitting it to be protectively inset from the surrounding surfaces of the anode housing 3.
The housings l and 2 are both molded inseparably to an anodized aluminum head fitting 10 which extends into the bottom of the boat. V-shapedfins 11 extend laterally from the fitting 10 to assure continued alignment of the electrode housings 3 and 4 under operating conditions. An anodized aluminum stud 12 is utilized to retain the housings 3 and 4 in place beneath the bottom of the boat. The lower end of the stud 12 is threaded into and epoxiedwithin the fitting l0, and the upper end is threaded for reception of a flanged nut which bears against the inner surface of the hull bottom. An O-ring seal 15 (FIGS. 2 and 3) seals the fitting 10 to the hull to prevent leakage around the fitting l0 and the stud 12. This seal should be able to withstand static compression and a wide temperature variation, and be impervious to the effects of lube oil, gasoline, engine exhaust and salt water.
Referring to FIGS. 2a and 3a a wire lead 20 extends through a bore 21 in the stud l2 and the head fitting 10 where it is soldered to a brass eyelet 22. The anode electrode 5 is preferably made of a substrate of titanium, niobium or tantalum plated with platinum. The eyelet is utilized to facilitate electrical connection of the wire 20 to the electrode 5. The assembly is then potted by molding it within the housing 3 as illustrated in FIG. 2a. As the outer surface of the anode electrode 5 is the only surface exposed to the water, platinum plating may be confined to this area.
Leakage of water through the interior of the anode 1 is eliminated by potting the anode, its connecting wire 20 and the outer ends of the head fitting within the anode housing 3. A series of fingers 25 extend angularly from the fitting 10 into the plastic material forming the housing 3 to assure a secure mating between the two. In addition to permanently securing the anode electrode 5 in place within the housing 3, the potting of the electrical elements as described prevents any possible leakage of water into the boat through the channel 21 in the stud 12.
Referring to FIGS. 2b and 3b, the housing 4 of the reference electrode 2 comprises a base 30 which is molded to a head fitting 10. A coil 26, preferably a silver wire, is mounted within a channel 27 extending longitudinally through an upper portion of the housing base 30. The electrode wire coil should be sufficient size as to prevent surface polarization by the current it may be subjected to under operating conditions. One end of the coil wire becomes an electrical lead 28 which extends through a bore 29 drilled through the housing base 30 and the head element 10 after the aforementioned molding thereof. Lead 28 is silver soldered to an electrical lead 40 from a control circuit at a point within a cavity 31 in the head fitting 10. A suitable potting compound is then poured into the cavity 31 until the soldered junction is completely covered, to protect it from any water which may enter through the bore 29 and also prevent any leakage of water into the boat through the interior of fitting It].
The reference electrode housing includes a separate cover 32 which is molded separately and set in place as illustrated after installation of the reference electrode coil 26. A series of holes 33 may be molded or drilled in the cover 32 to provide access for the seawater to come in contact with the reference electrode coil 26.
The wires 20 and 30 leading from the anode and reference electrode respectively may be connected to any appropriate cathodic control circuit, such as that presently incorporated in a cathodic protection device sold by the assignee hereof under the trademark Mercathode.
While the principles of the invention have been described in connection with the above specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.
1. A reference electrode for a marine cathodic protection device, comprising:
a wire electrode mounted in said housing, and means for mounting said housing to the hull of a boat, in cluding means providing for connection of said wire electrode to a control circuit for the cathodic protection device,
said housing comprising a body of erosion and corrosion resistant electrically insulating material, said body being molded about a metallic structural support member including a first portion having a plurality of radially extending fins adapted to engage the hull of a boat for maintaining said support member on the hull in a preselected rotational position, and a second portion having a plurality of fingers extending radially into the molded position of said body for maintaining said body in position on said support member,
said housing having a recess therein receiving said wire electrode, and a cover mounted over said recess, said body and cover having an air foil camber along its longitudinal axis and said cover having a plurality of passages therethrough communicating with said recess.
2. The device of claim 1 wherein said structural member has a recess therein, said mounting means further includes a threaded tubular member communicating with said recess and connected to said structural supporting member and adapted to extend through the hull of a boat to retain said reference electrode in preselected position upon the hull; and wherein said means for connection of said electrode to a control circuit includes a lead extending through said tubular member and into said recess, means connecting said lead to said electrode within said recess and a potting compound filling said recess around said connection and sealing the connection of said body and tubular member against the passage of water therethrough.
3. The device of claim 2 further including resilient means disposed adjacent said body and around said tu bular member and adapted for sealing engagement between said molded body and the hull of a boat.