US3497444A

US3497444A - Anode structure

Info

Publication number: US3497444A
Application number: US630894A
Authority: US
Inventors: Harold K Paiton
Original assignee: Sinclair Research Inc
Current assignee: Sinclair Research Inc
Priority date: 1967-04-14
Filing date: 1967-04-14
Publication date: 1970-02-24
Anticipated expiration: 1987-02-24

Description

Feb. 24,1970

H. K. PAITONI 3,497,444 ANODE STRUCTURE Filed April 14,1967

FIG. I

FIG. 2

INVENTOR HAROLD K. PAITON BY 24%; m /fmw ATTORNEYS United States Patent 3,497,444 A'NODE STRUCTURE Harold K. Paiton, Forest Hills, N.Y., assignor to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware Filed Apr. 14, 1967, Ser. No. 630,894 Int. Cl. C23f 13/00 U.S. Cl. 204196 4 Claims ABSTRACT OF THE DISCLOSURE A sacrificial anode and mount structure which includes: a bushing having an open center; a rod of electrical conductive material passing through the center of said 'bushing; an electrical conducting anode body affixed to one end of the rod spaced along from the bushing and enclosing the end of the rod; a spacer sleeve of non-permeable solid dielectric material mounted on the rod between the anode and bushing, butting the anode body and circled by the bushing at the opposite end of the sleeve; sealing means bonding the surfaces of the sleeve to the adjacent surfaces of the anode body, the rod, and the bushing means at the end of the rod remote from the anode body; and means on the end of the rod remote from the anode body for applying an electircal potential to the rod.

This invention relates to the inhibition of corrosion and, in particular, to a sacrificial anode structure suitable for employment under submerged conditions in a steam boiler or the like.

As is Well known, the corrosion of certain metals, such as ferrous metals in contact with water, particularly under elevated temperatures, can be materially reduced by submerging an electrode in the liquid and placing a potential on the electrode which is positive with respect to the potential on the skin on the boiler whose corrosion is to be inhibited. Such anode structures typically are sacrificial in that during the process of eliminating corrosion of the boiler, the anode goes into solution. For this reason the anode must be replaced from time to time in order to insure continued corrosion protection. As a matter of convenience, it is desirable to mount the anode on a support device which is secured to the side, top or bottom of the boiler being protected and which is constructed so that it is removable through an aperture in the boiler in which the support is mounted, thus permitting replacement of the anode from time to time, as required. It is necessary that the support itself include insulation between the anode and the wall of the boiler and that it permits electrical connection to be made through the wall of the boiler to the anode, which is likewise insulated from the boiler. When, for one reason or another such as convenience in locating the anode support for ready removability it is necessary to have the anode support entirely submerged, the life of the sacrificial anode structure is seriously limted by the durability of the insulation between the anode, including its electrical connections to the exterior, and the boiler wall. Even where insulating materials are chosen which are resistant to corrosion and resistant to penetration by hot water, they are in contact with an electrode structure which tends to dissolve. This dissolution of the electrode structure frequently occurs adjacent to the insulation, working beneath the insulation so that the insulation becomes weakened. Moreover, portions of the anode structure which are connected electrically to the exterior of the boiler and which are protected from attack by the insulation are thus exposed and frequently corroded through long before the main portion of the anode is used up.

It is the primary object of this invention to provide a combined anode and support structure of the type referred to above which is so constructed as to prevent electrolytic attack upon the anode and its electrical connection to the exterior where these are relatively thin. Thus, dissolution of the anode structure is predetermined to occur where that structure is more massive, thereby prolonging the useful life of the device.

In general, this invention comprises a sacrificial anode and support structure in which an open center bushing is provided for mounting the support through an aperture in a boiler wall and in which the metal anode is afiixed on the end of a rod which serves as a conductor passing through the bushing. A spacer sleeve of a solid dielectric material, which is non-permeable to water at elevated temperatures, is mounted on the rod passing through the bushing at one end and abutting the anode body at its other end, which is spaced a short distance from the nearer end of the bushing. Where the spacer sleeve butts the anode body, the anode body is peripherally dimensioned such that it extends entirely about the rod outwardly a greater distance than does the spacer sleeve. A sealant is coated between the anode body and sleeve where these butt, between the sleeve and rod along the length of the rod beneath the sleeve, and between the bushing and the sleeve along the length of the sleeve beneath the bushing, such that an impenetrable barrier is provided against water penetration between the sleeve and anode body, between the sleeve and the rod, and between the bushing and the sleeve. At its end remote from the anode body, the rod is provided with means for mounting an electrical connection to the rod.

Thus it will be apparent that the electrode structure provided by this invention is employed by inserting the structure, anode body first, through a suitable aperture in the side or bottom of the boiler to be protected, up to a point at which the bushing can be secured in the aperture, for example, by threaded engagement. Thereafter a source of potential is connected to the exposed end of the rod and to the skin of the boiler such that the anode body thereby is placed at a positive potential with respect to the skin of the boiler. The potential difference between the anode and the skin of the boiler must be greater than the difference between the electrochemical potentials (EMF) of the anode and boiler skin.

For a more complete understanding of the practical application of this invention reference is made to the appended drawings in which:

FIGURE 1 is a fragmentary vertical section through the side wall of a boiler illustrating a sacrificial anode constructed in accordance with the present invention connected to provide corrosion protection for the boiler; and

FIGURE 2 is an enlarged vertical section of the anode body and support structure shown in FIGURE 1.

Referring more particularly to FIGURE 1, an electrode 10 extends into superheated water 11 through a threaded circular aperture 12 on a boiler wall 13 and threadedly engages boiler wall 13. Boiler wall is also drilled and tapped at a point 14 to accept a threaded rod 15 on which ride a square nut 16 and a locking hexagon nut 17. Boiler wall 13 is maintained at the negative potential of a direct current source 18 by means of a lead 19, one end of which is connected to the negative terminal of source 18 and the other end of which terminates in a lug 20 which is locked between

nuts

16 and 17. The positive terminal of source 18 is connected through a switch 21 to 9. lug 22 which is locked between a pair of nuts, 23 and 24, which threadedly engage a threaded end of brass rod 25 forming part of electrode 10.

As more clearly illustrated in FIGURE 2, rod 25 passes axially through an insulated washer 26, a threaded brass bushing 27, and a spacer sleeve 28 to threadedly engage a brass anode body 29. Insulating washer 26 is preferably made of neoprene or some other suitable resilient material which is capable of withstanding the extreme heat of boiler wall 13 as well as electrically insulating square nut 24 from bushing 27. Bushing 27 is provided with an open center for mounting the support structure of anode body 29 in circular aperture 12, that is, for mounting rod 25 and spacer sleeve 28. Bushing 27 also has hexagon crown 30 so that the leverage of a wrench or similar tool may be applied to bushing 27 during the installation of electrode 10. Spacer sleeve 28, which is composed of fiber glass or some other solid electrical insultant which is non-permeable in water at elevated temperatures surrounds rod 25 and extends from insulating washer 26, through bushing 27 at one end, to butt anode body 29 at the other end. The diameter of anode body 29 is slightly larger than the diameter of spacer sleeve 28 where they butt. A sealant 31, such as fiber glass glue or silicon rubber sealant, is coated between anode body 29 and spacer sleeve 28, between rod 25 and spacer sleeve 28 along the length of the rod beneath the sleeve, and between the threaded bushing 27 and the spacer sleeve 28. Any electrolytic attack upon rod 25 as anode body 29 passes into solution will be prevented by sealant 31 and spacer sleeve 28.

In operation, electrode structure is inserted, anode body first, in aperture 12 until bushing 27 is threadedly secured in boiler wall 13. The positive terminal of electrical source 18 is connected through closed switch 21 and conducting rod 25 to anode body 29. Anode body 29 and rod 25 are suitably insulated from the boiler wall 13 by insulating spacer sleeve 28, sealant 31 and insulated washer 26. The negative terminal of electrical source 18 is directly connected to boiler wall 13 thereby causing an electrolytic action between positive anode body 29 and boiler wall 13 which will tend to inhibit corrosion of boiler wall 13. The electrolytic action which inhibits the corrosion of boiler wall 13 Will cause anode body 29 to go into solution and, as anode body 29 passes into solution, sealant 31 will prevent any seepage of liquid 11 beneath the spacer sleeve 28 where it would tend to erode rod 25. Thus, spacer sleeve 28 and sealant 31 combine to effect the dissolution of electrode 10 at anode body 29 where the electrode is most massive, thereby prolonging the useful life of the electrode.

It is claimed:

1. An anode and mount structure which includes: a bushing having an open center; a rod of electrical conductive material passing through the center of said bushing; an electrical conducting anode body affixed to one end of said rod spaced therealong from said bushing and enclosing said end of said rod; a spacer sleeve of nonpermeable solid dielectric material mounted on said rod between said anode body and bushing and butting said anode body and extending through said bushing at the opposite end of said sleeve; sealing means bonding substantially the entire surfaces of said sleeve to the adjacent surfaces of said anode body, said rod, and said bushing means; and means on the end of said rod remote from said anode body for applying an electrical potential to said rod.

2. An anode and mount structure according to claim 1 in which said spacer sleeve has transverse dimensions smaller than the corresponding transverse dimensions of said anode abutting said sleeve whereby said anode extends outwardly of said sleeve at the position at which said sleeve and said anode abut each other.

3. An anode and mount structure according to claim 1 in which said spacer sleeve is composed of fiber glass and said sealing means is fiber glass cement.

4. An anode and mount structure according to claim 1 in which said anode body is threadedly connected to said rod.

References Cited UNITED STATES PATENTS 393,072 11/1888 Marquand 204-196 892,626 7/1908 Selinger 174152 1,506,306 8/1924 Kirkaldy 204196 2,290,008 7/ 1942 Abell. 3,081,252 3/1963 Preiser et al. 204196 T. TUNG, Primary Examiner US. Cl. X.R.