US3421990A - Sacrificial anode - Google Patents

Description

United States Patent Ofifice 3,421,990 Patented Jan. 14, 1969 3,421,990 SACRIFICIAL ANODE William B. Penix, Northridge, Calif., assignor to Nancy Ann Penix Filed Apr. 28, 1966, Ser. No. 551,836 US. Cl. 204-197 Claims Int. Cl. (323i 13/00 This invention relates in general to sacrificial anodes of the type employed in an electrolytic system for preventing corrosion of metallic surfaces in contact with aqueous solutions or other electrolytes, and more particularly to a construction for such anodes, for use in swimming pools.

It is well known that upon the submerging of a metallic structure in aqueous solution, corrosive action is initiated. It is also known that the corrosion process is accompanied by the passage of a small electrical current between the metallic object and the aqueous solution in a manner which is similar in many respects to, but the reverse of the electroplating process. Such electrolytic corrosion is exceedingly damaging to steam boilers, ships hulls, dock pilings, anchor couplings and practically any metallic object which is in contact with such a solution for a relatively long period of time.

Electrolytic corrosion is a major problem in swimming pools as well. In the relatively high concentrations of chlO- rine and acid found in pool water the corrosive action on the pipes, filters and metal fittings is greatly accelerated. Generally, the pipes, conduits, filters, and associated fittings which are either buried below-ground, or hidden out of sight are made of copper or a similar metal, which is not subject to rapid corrosion in such aqueous medium. Unfortunately, the custom of plating the metal fixtures, hardware and fittings used in the pool itself prevents the use of the relatively unreactive metals, and has led to the use of the highly reactive iron-containing alloys. Despite the plating that is supposed to protect objects made of these alloys, corrosion remains a very serious problem in the typical home swimming pool.

Electrolysis, which results in electrolytic corrision, will always occur to some degree between metal objects emersed in an electrolytic solution. It is well known that dissimilar metals in an electrolyte normally assume an electrical positive-to-negative relationship, the metal being the higher on the electromotive series becoming the positive pole or anode, and other metal becoming the negative pole or cathode. By electrolysis the anode is dissolved within the solution leaving the cathode relatively unharmed. One method utilized in an attempt to resolve the problem of electrolytic corrosion of exposed metal parts is to expose to the corrosive medium an electrode made of a metal or metallic alloy having greater reactivity than the parts sought to be protected. Such a sacrificial anode is thus intentionally subjected to corrosion in order that the more valuable metal parts suffer no damaging change.

Employing the above principle in connection with the metallic fittings in swimming pools, a metallic material which is anodal to the metallic fitting to be protected is positioned adjacent each such fitting in the pool and in electrical connection with it. The exposed metallic fittings found in swimming pools are usually constructed of ferrous metals on which a thin finish of a material such as chrome is plated. A number of metals have greater reactivity than iron, but alloys of zinc are usually employed for sacrificial anodes used to protect such ferrous metalcontaining parts since zinc is readily available and relatively inexpensive as compared to most of the others. It is one object of this invention to provide such an anode, containing a relatively large volume of reactive material, which may be exposed progressively over a long period of time to the destructive effects of pool water.

As an anode is being dissolved, it becomes pitted and darkened and thus unsightly. Since the anode of this invention is to be employed in swimming pools where it will be observed by those using the pools or viewing them, it is desirable that such anode be constructed so that the resulting unattractiveness is hidden from view. Another object of this invention, therefore, is to sheath the portion of the anode which is exposed to view with a relatively non-reacting material, thereby shielding the corroding portion from view.

Another object is to provide for such an anode which can be manufactured simply and inexpensively.

A typical application of such an anode would be to protect the metallic drain grate and rope rings in swimming pools. It is desirable to be able to attach and remove the anode easily and yet to insure that the electrical connection between the grate or rings and the anode will remain secure at all times. Therefore, another object of this invention is to provide a fastening means to facilitate attachment of the anode to the metallic fitting thereby establishing a durable, yet easily releasable electrical connection between the two. Another object is to provide a universal fastening which can be applied to any of the existing pool fittings without need for their modification. Still another object is to construct the anode in such a manner that the corrosion process does not permit the fastening means to become loosened or detached and thereby allow the anode to lose contact with its metallic fitting. Another object is to provide a sacrificial anode which will maintain its form and attractive external appearance until substantially all of its corrosible contents have been exhausted.

Briefly, this invention comprises a continuous solid mass of zinc or other suitable anodal material intimately sheathed on its upper surface and sides and around the periphery of its lower surface with a continuous layer or series of layers of relatively non-corrosible material and having a band of the same or similar sheathing material across the unsheathed portion of its lower surface. A fastening means, preferably of the clip-on type is attached to the lower surface on the band of sheathing material by means of a non-corrosive electrically conductive screw, which passes through the band of sheathing material and is imbedded securely in the anodal material lying above the sheathing band. When mounted on the fitting to be protected by means of the clip fastener, the anode is suspended at a distance from the fitting with only its noncorrosible exterior exposed to view.

The novel features that are considered characteristics of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description, when read in connection with the accompanying drawings, in which:

FIGURE 1 is a perspective view of an anode of this invention;

FIGURE 2 is a longitudinal cross-sectional view of the anode of FIGURE 1, with the thickness of the outer layer of sheathing material greatly exaggerated;

FIGURE 3 is a view taken along line 3-3 of FIG- URE 2;

FIGURE 4 is a view similar to FIGURE 2 but showing the anode nearly exhausted, and with the thickness of the outer layer of sheathing material greatly exaggerated;

FIGURE 5 shows an anode as installed to a typical swimming pool grate; and

FIGURE 6 is a perspective view of another embodiment of the subject invention.

In FIGURES l, 2 and 3 there is shown an anode 10 having upper and lower faces 12 and 14, respectively. For descriptive purposes sides 16, 18, 20 and 22 complete the rectangular box-like configuration of this preferred embodiment. The reactive mass 24 of the anode 10 comprises the metallic material to be dissolved by electrolysis, such material in this instance being an alloy of zinc. Reactive mass 24 is in the form of a solid bar of such a suitable zinc alloy sheathed completely on its upper face 12 and sides 16, 18, 20 and 22 with a material which, in the presence of the reactive mass 24, is not subject to electrolysis. Any number of materials could be employed for the sheathing layer, and include the more noble metals, such as chromium and aluminum, any plastic or metal composition material, or any other material which effectively insulates the covered surface of the anode against the electrolytic process. Preferably the sheathing material is electroplated directly on the mass 24 in order to insure an intimate contact between mass 24 and the sheathing material itself. As will be seen, this contact substantially increases the longivity and usefulness of the anode and is highly desirable.

Face 14 is similarly sheathed around its periphery, and a center strip 26 of like sheathing material applied, thereby effectively connecting the sheathing covering sides 18 and 22 across face 14.

It is essential to the subject invention that the sheathing material covering the upper face 12, sides 16, 18, 20 and 22 and the periphery of the underside 14 be continuous, or at least that its several component parts be rigidly connected, and that strip 26 be continuous with or connected to the sheathing on sides 18 and 22 or the portion of the material covering the periphery of lower face 14 adjacent to those sides. The most effective method of accomplishing this end is to apply the sheathing material by means of electrolpating.

In practice, the anode 10 is sheathed quickly, simply, and inexpensively by masking two areas 24a, 2412 on the underside 14 with tape or other suitable liquid-repellent material, suspending it in an electroplating or anodizing tank, and plating or anodizing the exposed surfaces to the desired thickness, porosity, texture, hardness and color.

An electrically conductive fastening means, such as spring steel clip 28, is fixedly secured to strip 26 by means of screw 32 to permit rapid and secure attachment of the anode to the metallic fitting which is to be protected. Clip 28 and screw 32 are also coated with a non-corrosible sheathing material. FIGURE illustrates the method of attachment of clip 28 to a grate 30, which is used to pre vent the passage of sizeable foreign matter within the pool through the bottom drain and into the hydraulic apparatus of the pool.

In FIGURE 4 there is depicted an anode whose useful life has been nearly exhausted. Attacked only from within by the electrolyte, reactive mass 24 has been substantially dissolved away and cavities 36 and 38 have been formed above the unsheathed areas of what had been lower face 14. The outer portion of the mass 24 lying adjacent the protective coat of sheathing material is pitted and partially corroded, but remains generally intact. Similarly, a substantial portion of the reactive mass 24 lying in fluid-tight contact with the strap formed by center strip 26 remains intact, furnishing adequate internal support for screw 32 and maintaining fastening means 28 securely attached to the anode 10. It is important to note that without this unique transverse strap of fluid-tight construction the lower face 14 would be attacked immediately and quickly weakened to the point where all support for screw 32 would be lost.

In addition to furnishing means for securing the clip 28 to anode long after conventionally constructed anodes would have separated from their attachment means and been lost, the undissolved portion of mass 24 together with the unaffected layer of sheathing material -still substantially surrounding what is left of anode 10 furnishes external re-enforcement for the anode, retaining its outward appearance until the very end of the anodes usefulness.

It should be noted, also, that it is not necessary for the sheathing material to be of sufficient strength to support clip 28 and screw 32 by itself. Since the corrosive force of the pool water attacks the mass 24 where it is exposed, leaving the part adjacent the sheathing material, around the periphery of lower face 14 and above strip 26 structurally sound and integral until mass 24 is completely used up, the anode tends to maintain its own external form without requiring substantial support from the sheathing layer.

FIGURE 6 illustrates another of the many and varied forms in which the principles of the subject invention may be employed. Here the anode is essentially hemispherical in shape, with its entire domed upper surface 42 sheathed in suitable non-corroding shielding material. As in the first example the shielding material extends inwardly over the edge of the base to cover a relatively narrow band 44 around the periphery of the lower surface 46, and across the central region of the lower surface 46 to form a strip 48. Likewise as in the earlier example this strip 48 furnishes the seat upon which a clip 50 is mounted, and a screw 52 passing through strip 48 into the underlying reactive mass of the anode retains clip 50 in this position throughout the useful life of the anode.

Although only two embodiments of the subject invention have been described, it is to be understood that various changes and modifications may be made within the scope of the invention as it is defined in the claims which follow.

What is claimed is:

1. A sacrificial anode for the galvanic protection of cathodic metal objects in a fluid electrolyte comprising:

A reactive mass;

A substantially continuous sheath of relatively nonreactive material surrounding said reactive mass and in fluid-tight relationship with the outer surface thereof;

An opening in said sheath through which said mass is exposed to said fluid electrolyte;

A strap of relatively non-reactive material lying across said opening in fluid-tight relationship with the outer surface of said mass and contiguous with the portions of said sheath lying adjacent opposite sides of said opening;

Mounting means positioned on said strap for detachably mounting said anode on said cathodic metal objects and in electrical contact therewith; and

Connecting means connecting said mounting means to the portion of said reactive mass lying under said strap.

2. A sacrificial anode as described in claim 1 in which said strap is electrically conductive and is in electrical contact with said reactive mass.

3. A sacrificial anode as described in claim 1 in which said mounting means and said strap are electrically conductive and are in electrical contact with said reactive mass.

4. A sacrificial anode as described in claim 1 in which said mounting means and said connecting means are electrically conductive and said connecting means is in electrical contact with said reactive mass.

5. A sacrificial anode as described in claim 1 in which said sheath and said strap are in intimate contact with the outer surface of said reactive mass.

6. A sacrificial anode as described in claim 1 in which said sheath and said strap are in intimate contact with the outer surface of said reactive mass and said strap is electrically conductive.

7. A sacrificial anode as described in claim 1 in which said sheath and said strap are in intimate contact with the outer surface of said reactive mass and said mounting means and said strap are electrically conductive.

8. A sacrificial anode as described in claim 1 in which said sheath and said strap are in intimate contact with the outer surface of said reactive mass and said mounting means and said connecting means are electrically conductive.

9. A sacrificial anode as described in claim 1 in which said sheath and said strap are metallic materials deposited on said reactive mass by means of electroplating.

10. A sacrificial anode for the galvanic protection of cathodic metal objects in a fluid electrolyte comprising:

A reactive mass having a plurality of outwardly displayed faces;

A substantially continuous sheath of relatively nonreactive material surrounding said reactive mass and in intimate contact with said faces;

An opening in said sheath through which said mass is exposed to said fluid electrolyte, said opening being positioned on one of said faces so as to leave a continuous strip of said sheath surrounding said opening adjacent the periphery of said face;

A strap of relatively non-reactive material lying across said opening in intimate contact with the outer surface of said mass and contiguous with the portions of said strip of said sheath lying adjacent opposite sides of said opening;

Electrically conductive mounting means positioned on said strap for detachably mounting said anode on said cathodic metal objects and in electrical contact therewith; and

Connecting means connecting said mounting means to the portion of said reactive mass lying under said strap and in electrical contact with said mass,

References Cited UNITED STATES PATENTS 2,721,172 10/1955 Higgins et al 204 197 2,856,342 10/1958 Van Der Hoeven et al.

2,882,213 4/1959 Douglas 204-197 3,001,924 9/1961 Battis et a1. 4-197 3,012,958 12/1961 Vixler 204-290 3,354,063 11/1967 Shutt 204--197 FOREIGN PATENTS 1,081,845 6/ 1954 France.

JOHN H. MACK, Primary Examiner.

US. Cl. X R.

Claims (1)

1. A SACRIFICAL ANODE FOR THE GALVANIC PROTECTION OF CATHODIC METAL OBJECTS IN A FLUID ELECTROLYTE COMPRISING: A REACTIVE MASS; A SUBSTANTIALLY CONTINUOUS SHEATH OF RELATIVELY NONREACTIVE MATERIAL SURROUNDING SAID REACTIVE MASS AND IN FLUID-TIGHT RELATIONSHIP WITH THE OUTER SURFACE THEREOF; AN OPENING IN SAID SHEATH THROUGH WHICH SAID MASS IS EXPOSED TO SAID FLUID ELECTROLYTE; A STRAP OF RELATIVELY NON-REACTIVE MATERIAL LYING ACROSS SAID OPENING IN FLUID-TIGHT RELATIONSHIP WITH THE OUTER SURFACE OF SAID MASS AND CONTIGUOUS WITH THE PORTIONS OF SAID SHEATH LYING ADJACENT OPPOSITE SIDES OF SIDE OPENING; MOUNTING MEANS POSITIONED ON SAID STRAP FOR DETACHABLY MOUNTING SAID ANODE ON SAID CATHODIC METAL OBJECTS AND IN ELECTRICAL CONTACT THEREWITH; AND CONNECTING MEANS CONNECTING SAID MOUNTING MEANS TO THE PORTION OF SAID REACTIVE MASS LYING UNDER SAID STRAP.

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