US2910421A

US2910421A - Electrolytic system

Info

Publication number: US2910421A
Application number: US676033A
Authority: US
Inventors: Rolland C Sabins
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-08-02
Filing date: 1957-08-02
Publication date: 1959-10-27
Anticipated expiration: 1976-10-27

Description

Oct. 27, 1959 R. c. SABINS ELECTROLYTIC SYSTEM 2 Sheets-Sheet 1 Filed MI. 2, 1957 FIG.

FIG. 8

.s fl s RN Y E 0 D a M 2 m I AM a m Oct. 27, 1959 R. c. SABINS 2,910,421

' ELECTROLYTIC SYSTEM Filed Aug. 2, 1957 2 Sheets-Sheet 2 INVENTOR. ROLLAND C. SABINS a z/M219, l M M25 ATTORNEYS nited States Patent 6 ELECTROLYTIC SYSTEM Rolland C. Sabins, San Diego, Calif.

Application August 2, 1957, Serial No. 676,033

6 Claims. (Cl. 204--197) The present invention relates to electrolytic systems and apparatus therefor and more particularly to electrolytic system and apparatus therefor for preventing galvanic dissolution, i.e., by way of cathodic protection. The present invention is an improvement in and a continuation-in-part of my co-pending application Serial Number 595,932, filed July 5, 1956, now abandoned.

It is well known that immersion in an electrolytic solution of dissimilar metals in electrical interconnection will result in galvanic dissolution of the more anodic metal. This characteristic galvanic dissolution has been a particularly serious and costly problem, for example, to ship owners, because of the high maintenance costs which result from corrosion of the underwater surfaces and underwater fittings such as those fittings of a ships hull.

Although the corrosion problem is generally associated with steel ship hulls, there have been many undesirable galvanic interactions between other parts of the ship, and ships in which wooden hulls or other nonmetallic ship hulls were employed. For example, in a typical wooden naval vessel, there has been galvanic dissolution of the steel stern iron, the bronze propellers or screws, the screw struts, the shaft log castings, the copper plates for grounding electronic equipment, the housing for the transducers of the echo sound gear. In many cases, these hull fittings or cathodes and anodes are, in effect, electrically interconnected by the nonmetallic hull itself after a period of time, by reason of the increasing conductivity of such hull caused by the absorption of salt and salt water over a period of time. In other cases, there is an actual internal interconnection provided within the hull of these various components to thereby provide a common ground to reduce radio noise and electronic interference. These interconnections of the hull components thus provide a galvanic couple, and undesirable galvanic interaction, and consequently electrolysis has resulted.

Heretofore, such underwater fittings of nonmetallic hulls were either not protected whatsoever against this electrolysis, or else there was a limited form of protection provided, for example, by the direct coupling of a sacrificial anode, usually Zine, to each such fitting. Thus mounted, numerous anodes were required to provide individual protection to each of the numerous fittings and there was also an uncontrolled dissipation of the anodes by virtue of their direct coupling with the fittings and hull. The anodes consequently were quite inetficient and had a relatively short service life.

The importance of controlled dissipation of the anode becomes apparent when it is realized that an anode, when connected with the metal to be protected, acts to generate a maximum flow of current through the conductor which connects it with the metal or cathode. This flow is often much more than is necessary to reduce or prevent galvanic activity at the metal to be protected, and therefore some means is needed for maintaining the flow of current at value just sufiicient to provide optimum protection, and thus prolong the service life of the ice anode. One means used in steel ships requires connection of the anode to the fitting by a circuit within the ship, and providing in that circuit a control rheostat or the like. By this means, the current value may be adjusted by the rheostat.

However, since the available electric potential of an anode is relatively low, and since the maximum current output of the anode is controlled by various factors, not the least of which is the resistance of the internal ship circuit, it will be apparent that the lower this resistance, the lower will be the surface area of anode required for a given set of conditions. The importance of this desirable minimum resistance is particularly apparent when the water path resistance is high, as in fresh water as distinguished from sea water, or where the current demand for adequate cathodic protection is so high that the lead resistance must be extremely low to permit the high current to pass. The resistance must be so low that the reliance upon a conventional wiring system with its high lead to terminal resistances, would be inadvisable.

Accordingly the cathodic protection system of the present invention provides corrosion protection for the underwater metallic fittings of nonmetallic ships by a low resistance external bonding system, which system is itself protected from corrosion because it is located within the electrolyte, i.e., the water in which the ship floats. The various underwater metallic fittings are all coupled in the system to form, in effect, a common cathode of an electrochemical cell. By this bonding system, there is eliminated any necessity for an anode at each hull component to be protected, and greater streamlining of the hull contour is possible. A sacrificial anode or anode array, preferably magnesium alloy, is carried externally of the hull to form the other plate of the electrochemical cell, and these two plates are coupled through a control panel, embodying the rheostat, within the ship to permit regulation ofcurrent flow in the circuit when desired. The resistance of the circuit including the bonding system is a fraction of conventional wiring systems, and more efiicient utilization is made of the available anode.

Although, as was pointed out in the aforesaid copending application, a rheostat is necessary to maintain and can maintain the desired flow of current when conditions are normal or substantially so, nevertheless under certain conditions, the wood of a wooden hull is deleteriously afiiected. That is, often the paint is stripped from the hull, resulting in subjecting the wood, proper, to the deleterious effect of sea water, i.e., the wood is permitted to absorb water, and, also calcarious deposits are formed and fouling occurs, both of which are unsightly. I have discovered that, although the wood of the hull is an insulator, nevertheless when the anode touches the wood, under certain conditions, as for example when the demand for current is less than the dissociation by ionization, the voltage rises to such high value that hydrogen is generated behind the paint, causing the paint to peel. I have discovered that if the anode is suitably insulated from the wood, the deleterious effect, heretofore mentioned, is eliminated.

In carrying out the present invention, I attach a steel plate, preferably to depend from the keel of the hull. This steel plate, which extends longitudinally of the keel, is provided with a plurality of depending brackets. The anode sections are attached to these brackets but are insulated therefrom so as to insulate the anode from the wooden hull of the ship. Also, an insulated conductor leading from the anode includes a bolt which extends through the hull of the ship but is insulated therefrom in a novel manner.

The discussion and explanation of the present invention in connection with a sacrificial anode system of a wooden vessel is not intended to be limited, since the of cathodes into a common cathode by a bonding network which is itself part of the common cathode.

Further objects and advantages will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the invention is illustrated.

In the drawings:

Fig. 1 is a bottom view of the hull of a ship showing some of the components which are to be protected against electrolysis due to galvanic action;

Fig. 2 is a perspective view on a larger scale looking upwardly from underneath the hull of a ship and showing a preferred form of connecting the anode sections to the hull;

Fig. 3 is a perspective view on a still larger scale showing the mounting bracket and saddle for supporting one end of an anode section;

Fig. 4 is a perspective view showing the electrical connection from an end of the anode array to the conductor rod which extends through the boat and which leads to the rheostat;

Fig. 5 is a cross-sectional view of the electrical coupling which forms a part of the conductor, connecting the anode with the rheostat, and which is used for insulating the conductor from the hull of the ship;

Fig. 6 is a cross-sectional detailed view of the conrolled circuit electrical conductor leading from the rheostat to the bonding strip;

Fig. 7 is a detailed View in elevation of the brush connection to a screw shaft; and

Fig. 8 is a diagrammatic view of the electrolytic system.

Referring more in detail to the drawings, the hull of the ship is indicated at 20, the keel thereof being shown at 22. The rear end of the keel angles rearwardly upwardly, as is more clearly shown in Fig. 2. A steel plate 24 is suitably secured to the underside of the an gling portion of the keel; this plate 24 extends longitudinally of the keel. A series of brackets 26 are welded to the steel plate 24, and are disposed at spaced intervals as is more clearly shown in Fig. 2. These plates are preferably U shaped including legs 28 and a connecting yoke 30. The anode or anode array 32 is preferably formed of a plurality of elongated sections 34 of sacrificial metal such as Zinc or magnesium alloy. In the sections 34 each includes a plurality of rods or bars extending entirely through the same, the ends of the bars being shown at 36, and these ends extend longitudinally beyond the sacrificial material.

Suitable insulating material surrounds the bars 36 and such insulating material is herein shown as rubber hose 38. The hose 38 rests upon a saddle 40, and this saddle is secured to the yoke 30 of the bracket 26 by bolts 42. The ends of rods or bars 36 are welded to the confronting ends of the next adjacent bars of the next anode section. Thus all of the anode sections are connected in parallel circuit relation to form the anode or anode array 32. It will be understood that the ends of the sections of sacrificial material 34 are spaced a sufficient distance from the bracket 26 so that the hose 38 may be moved a sufficient distance to bare the ends of the rods 36 for the purpose of welding the confronting ends of these rods. A bridge 44 is suitably secured to the rods 36 at one extreme end of the anode 32. This bridge 44 includes a lug 46 which receives the end 48 of a conductor 50. The conductor 50 is connected to one end 52 of a rheostat 54. The other end of the rheostat 56 is connected by a conductor 5'8 to a bonding strip 68. All of the metallic parts which are subject to electrolysis, due to galvanic action, are connected to this strip 60, such parts being shown herein, for example, as a steel transducer housing 62 used for conventional echo sounding gear, a usual starboard propeller or screw assembly 64, a similar port screw assembly 66, starboard rudder assemblies 68', the plate 24, and other parts not shown, for example, the ground for radio and electronic gear disposed inside the vessel.

The through-hull fitting 70, through the hull 20 and which forms a part of the conductor 50 which connects the anode with the rheostat, includes a rod 72 having a head at the bottom thereof shown at 74. This head is disposed below the hull and is drilled as at 76 to receive the end 78 of the wire 80 forming that part of the conductor which connects the strap 44 with the rod 72. The end 78 of the wire 80 extends into and is silver soldered to the drilled socket 76; likewise the end 48 is silver soldered in the hole formed in the lug 46. The wire 80 is covered with insulation 82 and the

ends

48 and 76 at their respective couplings are taped with suitable waterproof electric tape.

The rod 72 extends upwardly through a metallic sleeve 84. This sleeve 84 extends through an opening 86 at the bottom of the hull and is provided with a head 88 which bears against the bottom of the hull 20, oakum 90 being interposed between the head 88 and the bottom of the hull to prevent leakage by the head through the opening 86. The central opening 92 in the sleeve 84 is of some what larger diameter than the diameter of the rod 72 so as to receive a rubber hose 94 at the bottom thereof, and the space between the bolt 72 and the inner surface 92 of the sleeve is filled with an air-hardening epoxy material 96. The upper exterior end of the sleeve 84 is threaded as at 98 and is clamped in position by a nut 100, a washer 102 being interposed between the top surface of the bottom wall of the hull and the bottom of the nut 100. A wire 104 is suitably secured to the rod 72. This wire 104 is connected at its other end to the end 52 of the rheostat 54, and forms a part of the conductor 50. Sleeve 84, and consequently nut and washer 102 are connected to bonding strip 60.

The through-hull conductor and conductor wire leading from the rheostat 54 and wire 58 to the bonding strip 60 is shown in Fig. 6. It includes a bolt 106 with a generous cross-section similar to rods 72, such as one inch. This bolt is disposed through the hull of the vessel in a watertight manner. Bolt 106 carries an external head 108, to which is silver soldered the bonding strip 60 and a washer 112, bolt 106 being bored out at the other or inner end to accommodate a heavy copper cable 58, such as 4/0 T.W., stranded copper cable. Cable 58 is silver soldered in position. A washer 114, nut 116 and locknut 118 secure bolt 106 in position, and cotton or oakum caulking 120 is provided, as illustrated, to prevent water leakage past bolt 106. By this construction it will be seen that a very low electrical resistance connection is provided between the rheostat and the bonding strip.

The various fittings to be protected are connected directly to the bonding strip 60 by low resistance conductors. The electrical connection of the bonding strip 60 to the normally rotating screw shaft is by a carbon brush assembly 122 which is silver soldered to the V- strut 124 at its apex. Assembly 122 carries a heavy carbon brush 126 which rides upon the shaft as illustrated in Fig. 7. Thus current may pass from the shaft, through assembly 122, through strut 124, and then to the bonding strip 60 which is electrically connected with the strut by low resistance conductor, all parts being silver soldered to one another.

By reason of the connection of all of the fittings to the bonding strip, electrolysis prevention is provided to all the various metallic components of the vessel, and these components are externally bonded to provide a common cathode with minimum electrical resistance to thereby drive maximum effectiveness from the operation of the anode, the bonding being preferably by fusion interconnection except at movable or non-fitting inner connections such as those between brush and screw shaft.

It has also been, discovered that the bonding strip can be utilized as the ground for the electronic systems of the ship and thus dispense with the wide area plates heretofore deemed necessary. The bonding strip, being narrow but relatively long, provides ample ground for any electronic system of the ship. The dispensing with the large copper plates, heretofore deemed necessary, eliminates the creation of dry rot which ordinarily took place on the hull of the ship which was covered by the wide plates.

As previously stated, I have discovered that by insulating the anode from the wooden or nonmetallic hull of the ship and insulating the conductor leading from the anode to the rheostat from the hull of the ship, the deleterious efiect on the wood of over-polarization of the cathodic material has been completely eliminated. The bonded system or common cathode being in the controlled circuit, does not require insulation from the wood hull as the potential in this side of the circuit is maintained at the desired optimum which is safely below the stripping potential encountered in an uncontrolled circuit. Also, inasmuch as all of the cathodic material including the ground plate for the electric systems are connected to a common bonding strip, there is no longer any need for providing a separate ground plate for such electronic equipment.

While the form of embodiment herein shown and described constitutes a preferred form, it is to be understood that other forms may be adopted falling within the scope of the claims that follow.

I claim:

1. In a corrosion prevention system of the type for use on a non-metallic vessel normally floating in water and having a plurality of external metallic fittings subject to galvanic corrosion, a sacrificial anode structure mounted externally on the vessel below the water line, low resistance uninsulated conductor means mounted externally on the vessel below the water line and connecting all of said fittings into a composite cathode and additional means connecting said anode structure to said composite cathode to limit current flow between the com posite cathode and the anode to thereby establish a predetermined polarization level on the composite cathode.

2. A system as in claim 1 wherein said last named means includes low resistance means passing through the hull of the vessel and adjustable resistance means connected between the composite cathode and the anode structure to vary the current flow between the same.

3. A corrosion prevention system as in claim 1 wherein said last named means includes insulated low resistance conductor means passing through the hull of the vessel, the insulation serving to prevent the establishment of aconducting path to the hull of the non-metallic vessel from the conductor, and adjustable resistance means within the vessel connected to the conductor means to limit current flow in the conductor means.

4. In a corrosion prevention system of the type for use on a non-metallic vessel normally floating in water and having a plurality of external metallic fittings below the water line subject to galvanic corrosion, a sacrificial anode structure mounted externally on the vessel below the water line, low resistance uninsulated electrical conductor means mounted externally on the vessel below the water line and connecting all of said fittings below the water line into a composite cathode and additional means connecting said anode structure to said composite cathode to limit current flow between the composite cathode and the anode to thereby establish a predetermined polarization level on the composite cathode.

5. In a corrosion prevention system of the type for use on a non-metallic vessel normally floating in water and having a plurality of external metallic fittings below the water line subject to galvanic corrosion, an anode array assembly mounted on the hull of the vessel below the water line consisting of spacer means mounted on the hull, a plurality of elongated anodes: of a sacrificial metal, a rod-like element extending through each of the anodes, means connecting the rod-like elements to form the rod-like elements and the anodes mounted therein into a unitary anode structure, means to secure the rodlike elements to the spacer means to support the anodes in a spaced relationship with respect to the hull of the vessel, insulating means mounted on the rod-like elements for .insulating the rod-like elements from the spacer means, insulated low resistance conductor means passing through the hull of the vessel and connected to the anode array assembly, the insulation. serving to prevent the establishment of a conducting path to the hull from the conductor, and adjustable resistance means within the vessel connected to the conductor to limit current flow in the conductor means.

6. A corrosion prevention system as in claim 5 wherein the conductor means include a through-hull fitting comprising a metal sleeve having a flanged head thereon and having the other end extending into the, interior of the hull, a nut threadably engaging the portion of the sleeve extending into the hull and serving to clamp the sleeve to the hull, a conducting rod extending through the sleeve, insulating material insulating the rod from the sleeve, and a conductor connected to each end of the rod.

References Cited in the file of this patent UNITED STATES PATENTS 1,900,011 Durham Mar. 7, 1933 2,616,844 Klumb Nov. 4, 1952 2,762,771 Preiser Sept. 11, 1956 FOREIGN PATENTS 749,636 France May 8, 1933

Claims

1. IN A CORROSION PREVENTION SYSTEM OF THE TYPE FOR USE ON A NON-METALLIC VESSEL NORMALLY FLOATING IN WATER AND HAVING A PLURALITY OF EXTERNAL METALLIC FITTINGS SUBJECT TO GALVANIC CORROSION, A SACRIFICIAL ANODE STRUCTURE MOUNTED EXTERNALLY ON THE VESSEL BELOW THE WATER LINE, LOW RESISTANCE UNINSULATED CONDUCTOR MEANS MOUNTED EXTERNALLY ON THE VESSEL BELOW THE WATER LINE AND CONNECTING ALL OF SAID FITTINGS INTO A COMPOSITE CATHODE AND ADDITONAL MEANS CONNECTING SAID ANODE STRUCTURE TO SAID COMPOSITE CATHODE TO LIMIT CURRENT FLOW BETWEEN THE COMPOSITE CATHODE AND THE ANODE TO THEREBY ESTABLISH A PREDETERMINED POLARIZATION LEVEL ON THE COMPOSITE CATHODE.