US2992983A - Energized anode assembly iv - Google Patents

Description

July 18, 1961 H. S. PREISER ET AL ENERCIZED ANODE ASSEMBLY IV Original Filed Dec. 28, 1956 5 Sheets-Sheet 1 9 20w 20w :2 9 r J: a: 20 Ka; J

3 ANODE BALANCING CONTROL AND METER BOX Low Volfoge Rectifier Low ADJUSTABLE A C z' TRANSFORMER MW" INVENTORS HERMAN s. PREISER FIG FRANK E. COOK eoms H. TYTELL ATTORNEY July 18, 1961 H. s. PREISER ET A]. 2,992,983

ENERQIZED ANODE ASSEMBLY IV Original Filed Dec. 28, 1956 3 Sheets-Sheet 3 FIG. 4. 27

XQ-IIIIIII ll 2 3 ll/Ill, 'IIII/l/IIII/I/I/ 7/////////I/\ INVENTOR5 HERMAN s. PREISER FRANK E. COOK BORIS H. TYTELL A} L ATTORNEY United States Patent 5 Claims. (Cl. 204-196) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefor.

This application is a division of applicants copending application Serial No. 631,377, filed Dec. 28, 1956, now Patent No. 2,910,419, Oct. 27, 1959, for Energized An ode Holder Assembly.

This invention relates to cathodic protection of metals against corrosion, and more particularly to cathodic protection of the underwater hull of a surface ship, submarine or the like against corrosion.

Cathodic protection techniques for corrosion control of marine structures are gradually finding widespread acceptance in marine and naval fields. Briefly stated, cathodic protection is the use of an impressed direct current for reducing or suppressing electrochemical corrosion of a metallic structure immersed in an electrolyte by making the structure a cathode for the impressed current. The impressed current may be supplied by sacrificial galvanic anodes or by electrically energized anodes. This invention is primarily concerned with the latter system employing inert anode materials.

For a complete disclosure of the factors responsible for the corrosion of the underwater hull of a ship or like structure reference may be had to applicants above copending application Serial No. 631,377, now Patent No. 2,910,419, Oct. 27, 1959.

An examination of the factors responsible for the corrosion of the underwater hull of a ship, indicated to applicants that specific materials are needed for use in cathodic protection systems. The particular properties sought will depend on the end use of the material. In general, materials are needed which are nonconducting, alkali resistant, oXy-chloride resistant, have low permeability to water transmission under a potential gradient, low water absorbitivity, are nonreactive to sea water, have high strength, are impact resistant and are readily formed into a variety of shapes. Plastic materials because of their versatility lend themselves admirably for components of cathodic protection systems.

Briefly, the elements of a cathodic protection system consist of an anode; a cathode; a current source and external circuit; and measuring instruments.

The anode for impressed current systems may be a platinum-clad silver or copper rod, or an integral platinum or platinum-clad disc or gauze, a graphite rod or slab, or other shapes of inert materials such as lead and, lead-alloys and high silicon iron alloys. The anode must be mounted in suitable holders which must be dielectric, oxy-chloride resistant, and rugged.

The cathode of a cathodic protection system is the structure under consideration; in the instant case a ships hull. In order to-insure adequate current distribution from the anode, shield materials are mounted on the bull in the vicinity of the anode. These materials must adhere to steel, have low permeability to electro-osmosis, have alkali resistance, be tough and flexible, and have good dielectric properties.

The current source and external circuit implies the use of chemically resistant cable sheaths and suitable cable attachment to the anode with appropriate seals.

The measuring instrument used for determining the cathodic potential of the structure is the reference electrode. This sensitive element must be housed in a dielectric, nonreactive, streamlined casing which is fitted with suitable cable seals.

The instant invention is particularly concerned with holders for attaching and supporting rod-type, rectifier energized anodes on the hull of a ship; surface or submanne.

An object of this invention is to provide an improved anode holder for use in cathodic protection systems.

Another object of the invention is to provide a streamlined anode holder.

Another object of the invention is to provide an anode holder that is dielectric.

Another object of the invention is to provide an anode holder that is resistant to alkali reactions.

Another object of the invention is to provide an anode holder that is resistant to oxy-chloride reactions.

Another object of the invention is to provide an anode holder that is light in weight, low in cost and high in mechanical strength.

Another object of the invention is to provide an anode holder wherein all mounting hardware is insulated and isolated.

A further object of the invention is to provide an anode holder wherein the anode is protected against mechanical shock.

A further object of the invention is to provide an anode holder which assists in the distribution of current from the anode.

A further object of the invention is to provide an anode holder which provides relatively free and rapid circulation of an electrolyte between the anode and a cathode.

In general, the holder of the instant invention is constructed of a dielecetric material, such as, a glass or nylon reinforced plastic which has been shown by test to be resistant to electro-chemical reactions at the anode and cathode. Tests have shown that polyester resins resist oxy-chloride reactions occurring at the anode and epoxy resins resist alkali reactions occurring at the cathode. The holders can be readily molded to proper shape by casting in a mold or through a laminate lay-up process. The cloth or chopped reinforcing fiber content can be adjusted to achieve the requisite physical properties of high impact shock resistance. Where the holder lays against the hull, several coats (20 mils) of epoxy resin are applied on all holder surfaces touching or adjacent to the hull. The application of epoxy resin directly to the cured polyester forms an integral mass, chemically bonded, The nonmetallic plastic holder provides positive anode insulation. It is streamlined, is light in weight and low in cost. The holder is fastened by a welded stud arrangement on the hull. The nuts for the fastening studs are either recessed within the plastic so that they are covered over with an insulating putty or with plastic plugs, or if protruding from a flange on the holder, the nuts are covered with molded plastic caps.

Particular features of the instant invention that are uncommon to holders for platinum-clad anodes are:

(a) The platinum-clad anode rod is supported in its holder by means of suitable plastic polyester or rigid polyvinyl chloride spacers. The spacers are snug fitted on the rod prior to assembly and position the anode axially in its holder.

(b) The holder itself is symmetrical about its axis and is generally fabricated by a wet lay-up process. It can also be made in one piece. Two angle sections are bolted together on a web section with plastic nuts and bolts, such as, rigid polyvinyl chloride. A wide flange particular to this holder serves as a partial dielectric shield for assisting current distribution from the anode. A cylindrical section of the holder is recessed at intervals to receive the spacers supporting the anode rod. The spacers may be cemented in place for additional strength. The cylindrical web section is scalloped between spacers to allow for maximum seat water path from anode to hull. The holder and spacers are drilled for free flooding and rapid circulation of sea water around the anode.

(c) The platinum-clad anode rod has two features in connection with this type holder. The thimble end of the rod, otherwise exposed to the water, is covered with a polyester sleeve to doubly insure a waterproof joint between thimble and cladding on the anode rod. Further, a sharp bend required of the A inch diameter rod where the anode enters the hull is clad with extra thickness platinum so that the stretching of the outer fibers during the bend will not result in a weakness in the cladding integrity.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the several views thereof, and wherein:

FIG. 1 shows a schematic wiring diagram for an impressed current cathodic protection system in accordance with this invention;

FIG. 2 is a top plan view of a holder for a platinumclad rod anode in accordance with the instant invention;

FIG. 3 is a side elevational view, partly in section, of the anode holder of FIG. 2;

FIG. 4 is an enlarged transverse section taken substantially on line 4-4 of FIG. 3;

FIG. 5 is an enlarged transverse section taken substantially on line 5-5 of FIG. 2;

FIG. 6 is an enlarged detail, partly in section, showing an insulating cap for an otherwise free end of the platinum-clad anode; and

FIG. 7'is an enlarged perspective of one of a plurality of anode-holding discs shown in FIGS. 4 and 5.

Referring first to FIG. 1, which illustrates a cathodic protection system wherein an impressed current is supplied by rectifier energized anodes, the numeral 10 designates the hull of a surface ship protected by a plurality of anodes spaced around the sides and stern thereof. As pointed out in detail hereinafter, each of the anodes is shielded from the hull by a dielectric shield or blanket 11. Each of the anodes is connected by a conductor 12 to an anode balancing control and meter box 13, which purpose is for measuring current output of each anode and for balancing differences in line resistance. Control 13 is connected by a conductor 14 to the positive side of a low voltage rectifier 15, while the negative side of the rectifier is grounded to the hull of the vessel, by a conductor 16, thereby making the hull the cathode of the low voltage circuit. A pair of conductors 17a and 17b connect opposite sides of the rectifier to the low voltage A.C. output of electrical energy from an adjustable transformer 18 which is fed by an AC. input 18a. Reference electrodes 19 are suitably mounted on the hull at least twenty-five feet from the nearest anode and are connected to a suitable potentiometer, not shown, for determining the polarization of the hull. Based on readings taken by the reference electrodes, adjustment can be made in the transformer 18 to change the current output to the anodes to corre spond to the proper value. Reference electrodes (Ag AgCl) readings below --.80 volts require an increase in the anode current, and readings above .80 volts require a decrease in the anode current. The elastic circuits, illustrated in FIG. 1, are not per se a part of this invention and therefore need not be described in further detail. It being suflicient to state that by these circuits a controlled low voltage current flows from the rectifier to the several anodes and from these through the sea water to the hull and back to the rectifier.

Referring now to FIGS. 2-5, in accordance with the instant invention, the anode assembly, indicated generally by reference numeral 20, includes a holder 21, made of polyester resin reinforced with glass fiber, and in inert, rod anode 22 formed of a platinum-clad silver rod and supported by the holder. Between the holder and the hull It) of the ship is a thick rubber pad 23 and the neoprene dielectric shield 11. The rubber pad, which is of substantially the same horizontal contour as the base of the holder, insures proper fit of the holder over minor irregularities in the hull and it provides a measure of shock and vibration protection to the holder. The dielectric shield 11 is formed of sheet neoprene and it stabilizes and extends the current paths.

In practicing the invention, with an anode assembly measuring 1 x 5, a neoprene dielectric shield 11 measuring 6 x 10" x /8" thick gives excellent results in forcing anode currents out from the anode into surrounding sea water where resistance paths are more nearly uniform, resulting in substantially uniform distribution of anode currents over the hull of the vessel. This effectively reduces high current concentration near the anode with its deleterious efiects on existing paint coatings. In practice, the eifectiveness of the shield may be enhanced by applying a heavy coat of vinyl paint 2 to 3 feet out from the edges of the neoprene sheet.

The holder 21 includes two substantially identical members, each including a horizontal or base portion 21a, 3. web or vertical portion 21b and an arcuate or semi-cylindrical portion 21c. At each end and at a number of intermediate points, depending upon the length of the holder, the web portions of the holder are drilled and are clamped together (FIG. 5) by a bolt, lockwasher and nut assembly indicated generally by reference numeral 26. Each of the elements of the bolt, lockwasher and nut assemblies is formed by vinyl chloride or other suitable dielectric, corrosion resistant material.

Prior to clamping the web portions together, as just described, a plurality of spacers 27, with the rod anode mounted thereon, are located between the semi-cylindrical portions 210 of the holder. The spacers, which are formed of polyester laminate and cylindrical in shape, are drilled with a central opening 27a (FIG. 7) for passage of the rod anode therethrough and with additional openings 27b for passage of sea water as described hereinafter. One of the spacers is located directly above each of bolt assemblies 26 within mating recesses in the cylindrical portions of the holder, as shown in broken lines in FIG. 5. Between the spacers 27, the upper or cylindrical portions 210 of the holder are scalloped in both a horizontal (FIG. 2) and a vertical (FIG. 3) direction, and, as shown, there is provided a series of spaced holes 21d along the length of each of these members. The scallops and holes in the holder and the holes in the spacers eliminate excess material in the Way of the anode which reduces water resistance in the way of the anode thereby increasing current output at the anode.

As shown in FIG. 6, the outer end, right hand end (FIG. 2), of the platinum-clad anode is swaged and a silversoldered, platinum thimble 22a is sweated thereon. Then a coating or cap 22b of polyester resin is placed over this end of the anode. The inner end of the anode, not shown, is likewise provided with a platinum thimble, without the plastic cap, for connection with a female electrical fitting attached to a current-carrying cable, not shown but similar to that shown and described in applicants parent application Serial No. 631,377.

At the left end, as viewed in FIG. 3, and as shown in FIG. 4, the platinum-clad anode penetrates the hull of the ship through a stuffing tube 28 welded to the hull. The gland nut 28a of the stuffing tube is accessible for outboard adjustment. So as to accommodate the outboard end of the stuffing tube and packing gland, the base portion 21a and web portion 21b of the holder, the rubber pad 23 and the dielectric shield 11 are provided with aligned openings, as shown in FIG. 4. The stuffing tube per se is not a part of the instant invention and therefore need not be described in detail.

The assembled holder 21 with the rod anode 22 mounted thereon is attached to the hull by a plurality of corrosion resistant studs 30 welded to the hull, each of which studs is provided with a standard lockwasher 31 and a nut 32. The mounting hardware is then enclosed by a pair of holded housings 33 formed of epoxy-glass laminate and cemented to the base of the holder by a suitable waterproof, dielectric material. Each of the housings 33 is provided with a plurality of transverse partitions 33a (FIG. 2), one at each side of the nuts 32, which partitions confine an insulating mastic 33b (FIG. 5) surrounding each nut. To prevent excess water pressure from acting on the housing 33, the housing is provided with a plurality of free-flooding holes 33c (FIG. 2) in the top surface thereof.

During fabrication of the assembly, all machined and drilled surfaces of the holder are coated with polyester resin. After installation of the assembly on the hull, the space (FIG. 4) between the stuffing tube and the dielectric shield, the rubber pad and the base of the holder is filled with epoxy resin 28b. Also any otherwise exposed surface of the stuffing tube and gland nut are painted with a coat of epoxy resin. In this manner, no metal parts are exposed except the platinum anode, which anode is insulated and shielded from stray currents as pointed out heretofore.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and, although the invention has been illustrated and described in connection with particular details of construction and the particular materials specific to the instant embodiment of the invention, the details of construction and the particular materials may be modified and/ or interchanged without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. An anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising an inert anode, said anode being formed of a platinum-clad rod, a holder for the anode, said holder being formed of dielectric, anticorrosive, chemically resistant material, said holder including a pair of substantially L-shaped members each including a base portion for attachment to the hull, a web portion provided with predeterminedly spaced openings therein and an arcuate portion, clamping hardware formed of dielectric, anticorrosive material and passing through the spaced openings for clamping the web portions of the holder into a unitary structure, means for attaching the anode to the holder, said anode attaching means including a plurality of plastic discs mounted in spaced relation along the length of the platinum-clad rod and clamped between the arcuate portions of the holder by the said clamping hardware, and means for insulatedly attaching the base portions of the holder to the hull.

2. An anode assembly as set forth in claim 1 wherein the base portions of the holder are provided with a plurality of predeterminedly spaced openings therein, and wherein the means for attaching the holder to the hull includes a plurality of studs secured to the hull in the same predetermined spaced relation as the openings in the base portions of the holder for receiving the holder and a nut for each of the studs, and a plurality of polyester plastic housings attached to the holder for inclosing the attaching studs and nuts.

3. An anode assembly as set forth in claim 2 wherein the anode is mounted in the holder in spaced relation to the hull, and wherein the holder is formed with means therein facilitating substantially free flow of ambient sea. water to and from the anode.

4. An anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising, an inert anode, said anode being formed of a platinumclad rod, a holder for the anode, said holder being formed of dielectric, anticorrosive, chemically resistant material, said holder including a pair of substantially L-shaped members each including a base portion for attachment to the hull, a web portion provided with predeterminedly spaced openings therein, each of said web portions having an elongated concavity formed therein, the concavity in one web portion being juxtaposed to the concavity in the other web portion, clamping hardware formed of dielectric, anticorrosive material and passing through the spaced openings in the web for clamping the web portions of the holder into a unitary structure, means for attaching the anode to the holder, said anode attaching means including a plurality of plastic discs mounted in spaced relation along the length of the platinum-clad rod and mounted within the space formed between said juxtaposed concavities, and being clamped between said web by said clamping hardware, and means for insulatedly attaching the base portion of the holder to the hull.

5. An anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising, an inert anode, said anode being formed of a platinum-clad rod, a holder for the anode, said holder being formed of dielectric, anticorrosive, chemically resistant material, said holder in cluding a pair of substantially L-shaped members each including a base portion for attachment to the hull, a web portion provided with predeterminedly spaced openings therein, and an arcuate portion, the concave side of each of said areuate portions being juxtaposed to one another to form a space therebetween, clamping hardware formed of dielectric,-anticorrosive material and passing through the space openings in the web for clamping the web portions of the holder into a unitary structure, means for attaching the anode to the holder, said anode attaching means including a plurality of plastic discs mounted in spaced relation along the length of the platinum-clad rod and clamped between the arcuate portions of the holder by the said clamping hardware, and means 'for insulatedly attaching the base portion of the holder to the hull.

References Cited in the file of this patent UNITED STATES PATENTS 2,863,819 Preiser Dec. 9, 1958 2,878,173 Obermann Mar. 17, 1959 FOREIGN PATENTS 614,799 Great Britain Dec. 22, 1948

Claims (1)

1. AN ANODE ASSEMBLY FOR USE IN IMPRESSED CURRENT CATHODIC PROTECTION SYSTEMS FOR UNDERWATER PROTECTION OF THE HULLS OF SHIPS AND THE LIKE COMPRISING AN INERT ANODE, SAID ANODE BEING FORMED OF A PLATINUM-CLAD ROD, A HOLDER FOR THE ANODE, SAID HOLDER BEING FORMED OF DIELECTRIC, ANTICORROSIVE, CHEMICALLY RESISTANT MATERIAL, SAID HOLDER INCLUDING A PAIR OF SUBSTANTIALLY L-SHAPED MEMBERS EACH INCLUDING A BASE PORTION FOR ATTACHMENT TO THE HULL, A WEB PORTION PROVIDED WITH PREDETERMINEDLY SPACED OPENINGS THEREIN AND AN ARCUATE PORTION, CLAMPING HARDWARE FORMED OF DIELECTRIC, ANTICORROSIVE MATERIAL AND PASSING THROUGH THE SPACED OPENINGS FOR CLAMPING THE WEB PORTIONS OF THE HOLDER INTO A UNITARY STRUCTURE, MEANS FOR ATTACHING THE ANODE TO THE HOLDER, SAID ANODE ATTACHING MEANS INCLUDING A PLURALITY OF PLASTIC DISCS MOUNTED IN SPACED RELATION ALONG THE LENGTH OF THE PLATINUM-CLAD ROD AND CLAMPED BETWEEN THE ARCUATE PORTIONS OF THE HOLDER BY THE SAID CLAMPING HARDWARE, AND MEANS FOR INSULATEDLY ATTACHING THE BASE PORTIONS OF THE HOLDER TO THE HULL.

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