CA1154719A - Method for controlling 'end effect' on anodes used for cathodic protection and other applications - Google Patents
Method for controlling 'end effect' on anodes used for cathodic protection and other applicationsInfo
- Publication number
- CA1154719A CA1154719A CA000368658A CA368658A CA1154719A CA 1154719 A CA1154719 A CA 1154719A CA 000368658 A CA000368658 A CA 000368658A CA 368658 A CA368658 A CA 368658A CA 1154719 A CA1154719 A CA 1154719A
- Authority
- CA
- Canada
- Prior art keywords
- anode
- shield
- cylindrical
- adjacent
- spaced away
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims description 9
- 238000004210 cathodic protection Methods 0.000 title abstract description 7
- 230000000694 effects Effects 0.000 title description 12
- 239000004020 conductor Substances 0.000 claims abstract description 18
- 239000007788 liquid Substances 0.000 claims description 3
- 230000002093 peripheral effect Effects 0.000 claims description 3
- 230000004323 axial length Effects 0.000 claims 1
- 239000003792 electrolyte Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 239000010405 anode material Substances 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000004411 aluminium Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- LWUVWAREOOAHDW-UHFFFAOYSA-N lead silver Chemical compound [Ag].[Pb] LWUVWAREOOAHDW-UHFFFAOYSA-N 0.000 description 2
- 239000011244 liquid electrolyte Substances 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 241001357542 Cirrula Species 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000010137 moulding (plastic) Methods 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 150000002843 nonmetals Chemical class 0.000 description 1
- 239000002674 ointment Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000001012 protector Effects 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000000565 sealant Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004901 spalling Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S204/00—Chemistry: electrical and wave energy
- Y10S204/07—Current distribution within the bath
Abstract
A B S T R A C T
'Necking' of elongated cathodic protection anodes is obviated or reduced by means of a non-conductive shield placed around the periphery of the anode, but spaced away from the surface of the anode at the end at which it is connected to a conductor cable. The gap between the shield and the electrode surface is generally in the range of 15 - 30% of the radius of curvature of the electrode surface.
The shield may extend over, but be spaced away from, the end surface of the electrode also.
'Necking' of elongated cathodic protection anodes is obviated or reduced by means of a non-conductive shield placed around the periphery of the anode, but spaced away from the surface of the anode at the end at which it is connected to a conductor cable. The gap between the shield and the electrode surface is generally in the range of 15 - 30% of the radius of curvature of the electrode surface.
The shield may extend over, but be spaced away from, the end surface of the electrode also.
Description
~ 7~1~
"Method for controlling 'end effect' on anodes used for cathodic protection and other appllcatlons~' The present invention relates to improvements in the performance of anodes made of metal~, semi-conductors and non-metals.
An anode is an electrode at which oxidation occurs and/or is the electron-emitting electrode.
Depending on the application and anode material, the mass of the anode d~creases at various rates during its operation, thus affecting the perfc,rmance and the life of the anode.
Anodes can be used as sacrificial or impressed current anodes for cathodic protection and other industrial processe~. All such anodes, both of the sacrificial and of the impressed current type, used in liquid electrolytes are subject to consumption regardless of what material the anode is made from.
In both cathodic protection and plating processes the anode is in many instances completely immersed in the electrolyte and, consequently, the electrical conductor (cable for example) connecting the anode with the cathode,'directly or 'through ~he current supply unit, is also expo~ed to the electrolyte. The electrical conductor and the connection between the anode and the electrical conductor must be protected from the chemi~al and electrochemlcal effect~ of ~he electrolyte.
~1 54~7
"Method for controlling 'end effect' on anodes used for cathodic protection and other appllcatlons~' The present invention relates to improvements in the performance of anodes made of metal~, semi-conductors and non-metals.
An anode is an electrode at which oxidation occurs and/or is the electron-emitting electrode.
Depending on the application and anode material, the mass of the anode d~creases at various rates during its operation, thus affecting the perfc,rmance and the life of the anode.
Anodes can be used as sacrificial or impressed current anodes for cathodic protection and other industrial processe~. All such anodes, both of the sacrificial and of the impressed current type, used in liquid electrolytes are subject to consumption regardless of what material the anode is made from.
In both cathodic protection and plating processes the anode is in many instances completely immersed in the electrolyte and, consequently, the electrical conductor (cable for example) connecting the anode with the cathode,'directly or 'through ~he current supply unit, is also expo~ed to the electrolyte. The electrical conductor and the connection between the anode and the electrical conductor must be protected from the chemi~al and electrochemlcal effect~ of ~he electrolyte.
~1 54~7
-2-The present inventlon i~ p~rticularly, but not exclu~ively9 directed to anodes (graphite, lead-silver etc.) oper~ting in so~called impres~ed current cathodic protection ~ystems, where the protected structure is rendered cathodic by connection to one or more anodes through a D.~. power source, both the protect~d structure and the anode(s) being within a common electrolyte, such as sea water or soil.
The invention is also applicable to so-called sacrificial anodeQ (aluminlumJ magne~ium, zinc), in which the ob~ect to be protected, such as a ship hull or ~tationary steel structure, ~orm5 a cathode which is directly connected to the anode by an electric~l conductor. A sacrificial anode i8 one which has a ~5 higher corrosion ra~e than the met~l to which it is connected in the electrolyte in which both are located.
It is a common practice to make the connection between an impressed current anode and an insulated cable or other conductor inside the anode and to ~eal off the connection with an inert nonoconductive m~terial to prevent ingress of the electrolyte. The anode-cable connection may be loc~ted a fsw inches or a few feet away from on2 end o the anode. In some sacrificial anodes, a small diameter steel core provides the connect~on over ~he e~tire le~gth of the ano&eO M~ny processes use elong~ted anodes, usually cylindrical anodes, and ln most cases the cqble or other conductor usually enters the anode ~t one end. In cathodic ~54~19 protection~ for example, the anodes may be 3 in.
to 6 ln. in diameter and 30 in. ~o 80 in. long.
The elongated shape of the anode, which has some theoretical and practical ~ustlfications, create~
increased concentration and di~charge of current at both ends of the anode. The high current density at the ends causes accelerated loss of anode material at these locations due to chemical and/or electrochemical reactions, or due to spalling. The current density is at a maximum in the region of any sharp edge, such as at the ~unction between a flat end and a cylindrical side surface of an anode.
In general, on cylindrical anodes the aotivity of the 'end effect' will be lowest when the anode h~s a radius to length ratio equal to 1~1. As the ratio changes, the activity of the 'end effect' increases at the smaller site.
On cyl~ndricàl anodes the 'e~d effect' will not only occur at the physical ends of the anodes, but also at the edge of any insulating clrcumerential obstruction around the cyllindr~cal part of the anode.
For example, if a tightly fitting plastic ring is installed at the middle of~-the anode, ~he-single anode -will behave like two individual anodes. The 'end effect' will be visible at both edge~ of the plastic ring. The inten~ity of the 'end effect' will depend on the length of the plast~c ring.
~ 7 ~
The result of an intensive 'end effect' at the edge of any circumferential obst~uction on the surface of the anode is called 'necking'. iNeck~ng', once triggered, reduces the diameter of the anode within a narrow band with increasing speed. Thls is because the curvature o the surface iQ continuously diminishing as the material of the anode is removed and i~ accompanied by increR~ing current density which increases the rate of removal. The result of 'necking' is that the anode fails prematurely at thi~
poi~t~
The ob~ecti~e of the present invention ~ 8 to greatly reduce or eliminate the 'end effect' and the 'necking'. This can be achieved by installing a circumferenti~l insul~ting obstruction spaced at a small, but su~stantial, distance from the surface of the a~ode at the area or are~s where high current denslty .-occurs.
Because of the space between the circumferential 2~ obstruction and the anode, the curren~ density discharged from the surface of the anode dimini~hes gradually a~ the anode disappears inside of the obstruction. The reduction of current output i8 CAU~ed by the fact that the ~urf~ce of the anode is prevented from discharging in the direction of the cathode.
The shield may b~ cylindrical or bell-shaped, and ha~e any cros section required to correspo~d to the shape of ~he anode. It m~y be open or closed at ~ne end, ~ 71 ~
with or without openings for release of gases and/or for cirrula~ion of electrolyte. The ~pace between the anode ~urface and the shield i5 substantial although small in relation to the radlus of curvature of the adjacent surface of the anode. The space between the shleld and the anode is preferably somewhat proportionate to the diameter of a cylindrical anode. Conveniently it may be 0.3 cm~ for anodes of 2.5 cm. di~meter, 0.3 cm. to 1.0 cm. for anodes of 2.5 cm. to 10 cm. diameter and 1 cm. to 2.5 cm. for larger anodes. Thus it is preferred that the initial gap between the ~hield and the ad~cent 3urface of the anode ~8 15 - 30% of the r~diu~ of curvature of the ~node surface.
For elongated anodes having a length of at least 12 times the diameter and having ~n a~ode-cable connector installed in on~ end of ~he anode, the ~xl~l length of the shield should be Approximately equ~l to the diameter of the anode. In ~ny caset the ~ower end of the shield should be approximately 2.5 - 5 cmsO
below ~he upper end of the cylindrLcal Isurface of a vertically arranged anode.
On ~hort, st~bby anodes havin~g a relati~ely large diameter of 15 cmsO or more, the Length of the 2S shield may~be reduced-to approximately ,Dne quarter of the anode diameter. Where a connéctor i~ located within the anode it is preferred that the lower edge of the ~hield ~hould extend beyond the end of the 4~ g connector. It becomes of less importance to have an actual overlap as the diameter of the anode is increased beyond 15 cms.
The shield permits the anode-cable connector to be closer to the end of the anode and thus allows a more complete consumption of the anode.
Without the shield the increased consumption of the anode material at the end region frequently results in premature failure of the anode around the connector.
In many cathodic protection applications the use of the shield would not only control the 'end effect' and 'necking' but would also permit the in-stallation of the anode-cable connection close to the end of the anode. This would facilitate machining and assembly.
Thus, in accordance with one broad aspect of the invention, there is provided a method of improving the performance of a generally cylindrical anode located in contact with a corrosive medium which comprises placing a shield formed of electrically non-conducting material around a short length of the cylindrical surface of the anode at at least one end of said anode, said shield being spaced away from said cylindrical surface by a substantial dis-tance which is small in relation to the radius of curvature of said cylindrical surface.
In accordance with another broad aspect of the invention there is ?rovided an anode assembly comprising an elongated body of electrically con-ductive material, an insulated conductor electrically connected to said body internally thereof and extending substantially axially out of one end of said body, a cup-shaped non-conducting shield member having an end portion surround-ing said insulated conductor and spaced away from the adjacent surface of said body and a generally cylindrical wall portion extending around but spaced away from the adjacent peripheral surface of said elongated body at at least one end thereof, said end portion and said cylindrical wall portion being arranged to ~154~i9 permit unrestrained access of liquid to the surfaces of said body facing said end portion and said cylindrical wall portion, said body projecting beyond said cylindrical wall portion.
Referring to the accompanying drawing it will be seen that an im-pressed current anode consists of a solid cylinder 1 of anode material, such as graphite, lead-silver or aluminium. A metal connector 2 connects the anode to a conductor cable 3, the insulation 4 of the cable being embedded in sealant 5. The protector shield is in the form of a plastic moulding, having a shield holder 6, a cover 7 and a cylindrical shield 8. The shield is formed with vents 9 for escape of gas.
The interrupted lines on the anode indicate the approximate future shape of the anode on discharge of current.
Extensive laboratory tests in liquid electrolytes were conducted using graphite, aluminium 6a-- :
;~ 5~9 and magnesium anodes. The aluminium and magnesium anodes were operated either as sacrificial anodes or parallel with graphite as impressed current anodes at low and at very high current densities. In all modes of operation accelerated corrosion at the protected location was avoided and the service life of the anode was consequently extended.
Tests were conducted to prove that the shield will perform equally well on any size of anode. The tests confirmed the effectiveness and per-formance of the shield installed on all types of anodes but particularly on the impressed current anodes discharging large amount of current.
.:
,. .: - ~ :
,, ,, :, ~ ..
.
~'' ' ~ '
The invention is also applicable to so-called sacrificial anodeQ (aluminlumJ magne~ium, zinc), in which the ob~ect to be protected, such as a ship hull or ~tationary steel structure, ~orm5 a cathode which is directly connected to the anode by an electric~l conductor. A sacrificial anode i8 one which has a ~5 higher corrosion ra~e than the met~l to which it is connected in the electrolyte in which both are located.
It is a common practice to make the connection between an impressed current anode and an insulated cable or other conductor inside the anode and to ~eal off the connection with an inert nonoconductive m~terial to prevent ingress of the electrolyte. The anode-cable connection may be loc~ted a fsw inches or a few feet away from on2 end o the anode. In some sacrificial anodes, a small diameter steel core provides the connect~on over ~he e~tire le~gth of the ano&eO M~ny processes use elong~ted anodes, usually cylindrical anodes, and ln most cases the cqble or other conductor usually enters the anode ~t one end. In cathodic ~54~19 protection~ for example, the anodes may be 3 in.
to 6 ln. in diameter and 30 in. ~o 80 in. long.
The elongated shape of the anode, which has some theoretical and practical ~ustlfications, create~
increased concentration and di~charge of current at both ends of the anode. The high current density at the ends causes accelerated loss of anode material at these locations due to chemical and/or electrochemical reactions, or due to spalling. The current density is at a maximum in the region of any sharp edge, such as at the ~unction between a flat end and a cylindrical side surface of an anode.
In general, on cylindrical anodes the aotivity of the 'end effect' will be lowest when the anode h~s a radius to length ratio equal to 1~1. As the ratio changes, the activity of the 'end effect' increases at the smaller site.
On cyl~ndricàl anodes the 'e~d effect' will not only occur at the physical ends of the anodes, but also at the edge of any insulating clrcumerential obstruction around the cyllindr~cal part of the anode.
For example, if a tightly fitting plastic ring is installed at the middle of~-the anode, ~he-single anode -will behave like two individual anodes. The 'end effect' will be visible at both edge~ of the plastic ring. The inten~ity of the 'end effect' will depend on the length of the plast~c ring.
~ 7 ~
The result of an intensive 'end effect' at the edge of any circumferential obst~uction on the surface of the anode is called 'necking'. iNeck~ng', once triggered, reduces the diameter of the anode within a narrow band with increasing speed. Thls is because the curvature o the surface iQ continuously diminishing as the material of the anode is removed and i~ accompanied by increR~ing current density which increases the rate of removal. The result of 'necking' is that the anode fails prematurely at thi~
poi~t~
The ob~ecti~e of the present invention ~ 8 to greatly reduce or eliminate the 'end effect' and the 'necking'. This can be achieved by installing a circumferenti~l insul~ting obstruction spaced at a small, but su~stantial, distance from the surface of the a~ode at the area or are~s where high current denslty .-occurs.
Because of the space between the circumferential 2~ obstruction and the anode, the curren~ density discharged from the surface of the anode dimini~hes gradually a~ the anode disappears inside of the obstruction. The reduction of current output i8 CAU~ed by the fact that the ~urf~ce of the anode is prevented from discharging in the direction of the cathode.
The shield may b~ cylindrical or bell-shaped, and ha~e any cros section required to correspo~d to the shape of ~he anode. It m~y be open or closed at ~ne end, ~ 71 ~
with or without openings for release of gases and/or for cirrula~ion of electrolyte. The ~pace between the anode ~urface and the shield i5 substantial although small in relation to the radlus of curvature of the adjacent surface of the anode. The space between the shleld and the anode is preferably somewhat proportionate to the diameter of a cylindrical anode. Conveniently it may be 0.3 cm~ for anodes of 2.5 cm. di~meter, 0.3 cm. to 1.0 cm. for anodes of 2.5 cm. to 10 cm. diameter and 1 cm. to 2.5 cm. for larger anodes. Thus it is preferred that the initial gap between the ~hield and the ad~cent 3urface of the anode ~8 15 - 30% of the r~diu~ of curvature of the ~node surface.
For elongated anodes having a length of at least 12 times the diameter and having ~n a~ode-cable connector installed in on~ end of ~he anode, the ~xl~l length of the shield should be Approximately equ~l to the diameter of the anode. In ~ny caset the ~ower end of the shield should be approximately 2.5 - 5 cmsO
below ~he upper end of the cylindrLcal Isurface of a vertically arranged anode.
On ~hort, st~bby anodes havin~g a relati~ely large diameter of 15 cmsO or more, the Length of the 2S shield may~be reduced-to approximately ,Dne quarter of the anode diameter. Where a connéctor i~ located within the anode it is preferred that the lower edge of the ~hield ~hould extend beyond the end of the 4~ g connector. It becomes of less importance to have an actual overlap as the diameter of the anode is increased beyond 15 cms.
The shield permits the anode-cable connector to be closer to the end of the anode and thus allows a more complete consumption of the anode.
Without the shield the increased consumption of the anode material at the end region frequently results in premature failure of the anode around the connector.
In many cathodic protection applications the use of the shield would not only control the 'end effect' and 'necking' but would also permit the in-stallation of the anode-cable connection close to the end of the anode. This would facilitate machining and assembly.
Thus, in accordance with one broad aspect of the invention, there is provided a method of improving the performance of a generally cylindrical anode located in contact with a corrosive medium which comprises placing a shield formed of electrically non-conducting material around a short length of the cylindrical surface of the anode at at least one end of said anode, said shield being spaced away from said cylindrical surface by a substantial dis-tance which is small in relation to the radius of curvature of said cylindrical surface.
In accordance with another broad aspect of the invention there is ?rovided an anode assembly comprising an elongated body of electrically con-ductive material, an insulated conductor electrically connected to said body internally thereof and extending substantially axially out of one end of said body, a cup-shaped non-conducting shield member having an end portion surround-ing said insulated conductor and spaced away from the adjacent surface of said body and a generally cylindrical wall portion extending around but spaced away from the adjacent peripheral surface of said elongated body at at least one end thereof, said end portion and said cylindrical wall portion being arranged to ~154~i9 permit unrestrained access of liquid to the surfaces of said body facing said end portion and said cylindrical wall portion, said body projecting beyond said cylindrical wall portion.
Referring to the accompanying drawing it will be seen that an im-pressed current anode consists of a solid cylinder 1 of anode material, such as graphite, lead-silver or aluminium. A metal connector 2 connects the anode to a conductor cable 3, the insulation 4 of the cable being embedded in sealant 5. The protector shield is in the form of a plastic moulding, having a shield holder 6, a cover 7 and a cylindrical shield 8. The shield is formed with vents 9 for escape of gas.
The interrupted lines on the anode indicate the approximate future shape of the anode on discharge of current.
Extensive laboratory tests in liquid electrolytes were conducted using graphite, aluminium 6a-- :
;~ 5~9 and magnesium anodes. The aluminium and magnesium anodes were operated either as sacrificial anodes or parallel with graphite as impressed current anodes at low and at very high current densities. In all modes of operation accelerated corrosion at the protected location was avoided and the service life of the anode was consequently extended.
Tests were conducted to prove that the shield will perform equally well on any size of anode. The tests confirmed the effectiveness and per-formance of the shield installed on all types of anodes but particularly on the impressed current anodes discharging large amount of current.
.:
,. .: - ~ :
,, ,, :, ~ ..
.
~'' ' ~ '
Claims (10)
1. A method of improving the performance of a generally cylindrical anode located in contact with a corrosive medium which comprises placing a shield formed of electrically non-conducting material around a short length of the cylindrical surface of the anode at at least one end of said anode, said shield being spaced away from said cylindrical surface by a substantial distance which is small in relation to the radius of curvature of said cylindrical surface.
2. A method according to claim 1 in which the initial gap between the surface of the shield and the adjacent cylindrical surface of the anode is 15 - 30%
of the radius of curvature of the anode.
of the radius of curvature of the anode.
3. A method according to claim 1 further comprising placing a shield of electrically non-conducting material to face the end surface of said electrode adjacent said cylindrical surface, said shield being spaced away from said end surface to permit access of said corrosive medium thereto.
4. A method according to claim 3 further comprising providing at least one gas escape passage for release of gas generated within the gap between said shield and the adjacent cylindrical surface of the anode.
5. An anode assembly comprising an elongated body of electrically con-ductive material, an insulated conductor electrically connected to said body internally thereof and extending substantially axially out of one end of said body, a cup-shaped non-conducting shield member having an end portion surround-ing said insulated conductor and spaced away from the adjacent surface of said body and a generally cylindrical wall portion extending around but spaced away from the adjacent peripheral surface of said elongated body at at least one end thereof, said end portion and said cylindrical wall portion being arranged to permit unrestrained access of liquid to the surfaces of said body facing said end portion and said cylindrical wall portion, said body projecting beyond said cylindrical wall portion.
6. An anode assembly according to claim 5 wherein said end portion of said shield member is flat, facing the end surface of said body.
7. An anode assembly according to claim 6 in which one or more gas escape passages are provided in said cylindrical portion adjacent its junction with said flat end portion.
8. An anode assembly according to claim 5 in which the cylindrical portion of said shield member is spaced away from the adjacent surface of said body, for entrance of liquid therebetween, by a distance equal to 15-30 per cent of the radius of curvature of said surface.
9. An anode assembly according to claim 5 in which the cylindrical portion of said shield overlaps the peripheral wall of said body by a distance of about 2.5 - 5 cm.
10. An anode assembly according to claim 5 in which the conductor is connected to the elongated body by means of a connector located axially within said body, the axial length of said cylindrical portion of said shield being sufficient to completely surround said connector.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8001783 | 1980-01-18 | ||
| GB8001783 | 1980-01-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154719A true CA1154719A (en) | 1983-10-04 |
Family
ID=10510736
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000368658A Expired CA1154719A (en) | 1980-01-18 | 1981-01-16 | Method for controlling 'end effect' on anodes used for cathodic protection and other applications |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4420382A (en) |
| CA (1) | CA1154719A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4773977A (en) * | 1987-04-16 | 1988-09-27 | A. O. Smith Corporation | Anode mounting construction for a water heater |
| GB8809750D0 (en) * | 1988-04-25 | 1988-06-02 | Beckswift Ltd | Electrical apparatus |
| US5290583A (en) * | 1992-04-02 | 1994-03-01 | David Reznik | Method of electroheating liquid egg and product thereof |
| US5571550A (en) * | 1993-01-22 | 1996-11-05 | Polny, Jr.; Thaddeus J. | Methods for electroheating food employing concentric electrodes |
| CA2132882A1 (en) * | 1993-09-23 | 1995-03-24 | David Reznik | Electroheating of food products using low frequency current |
| US5583960A (en) * | 1994-06-01 | 1996-12-10 | David Reznik | Electroheating apparatus and methods |
| US5741539A (en) * | 1995-06-02 | 1998-04-21 | Knipper; Aloysius J. | Shelf-stable liquid egg |
| US5897755A (en) * | 1997-01-31 | 1999-04-27 | Carsonite International Corporation | Cathodic protection test station |
| US5855747A (en) * | 1997-04-04 | 1999-01-05 | Aos Holding Company | Performance enhancing coating for water heater |
| US6174425B1 (en) * | 1997-05-14 | 2001-01-16 | Motorola, Inc. | Process for depositing a layer of material over a substrate |
| US6220200B1 (en) | 1998-12-02 | 2001-04-24 | Carsonite International | Line marker with locking mechanism |
| US6231743B1 (en) | 2000-01-03 | 2001-05-15 | Motorola, Inc. | Method for forming a semiconductor device |
| US8094784B2 (en) | 2003-04-25 | 2012-01-10 | Rapiscan Systems, Inc. | X-ray sources |
| US9208988B2 (en) | 2005-10-25 | 2015-12-08 | Rapiscan Systems, Inc. | Graphite backscattered electron shield for use in an X-ray tube |
| US10483077B2 (en) | 2003-04-25 | 2019-11-19 | Rapiscan Systems, Inc. | X-ray sources having reduced electron scattering |
| US8243876B2 (en) | 2003-04-25 | 2012-08-14 | Rapiscan Systems, Inc. | X-ray scanners |
| GB0812864D0 (en) | 2008-07-15 | 2008-08-20 | Cxr Ltd | Coolign anode |
| US8331535B2 (en) * | 2003-04-25 | 2012-12-11 | Rapiscan Systems, Inc. | Graphite backscattered electron shield for use in an X-ray tube |
| GB0525593D0 (en) | 2005-12-16 | 2006-01-25 | Cxr Ltd | X-ray tomography inspection systems |
| US9046465B2 (en) | 2011-02-24 | 2015-06-02 | Rapiscan Systems, Inc. | Optimization of the source firing pattern for X-ray scanning systems |
| GB0816823D0 (en) | 2008-09-13 | 2008-10-22 | Cxr Ltd | X-ray tubes |
| GB0901338D0 (en) | 2009-01-28 | 2009-03-11 | Cxr Ltd | X-Ray tube electron sources |
| WO2010141659A1 (en) * | 2009-06-03 | 2010-12-09 | Rapiscan Security Products, Inc. | A graphite backscattered electron shield for use in an x-ray tube |
| KR200464956Y1 (en) | 2010-10-22 | 2013-01-25 | 주식회사 우진 | Cathodic protection anode for preventing separation of electric wire |
| GB201210929D0 (en) * | 2012-06-20 | 2012-08-01 | E M & I Maritime Ltd | Apparatus and method |
| US10585206B2 (en) | 2017-09-06 | 2020-03-10 | Rapiscan Systems, Inc. | Method and system for a multi-view scanner |
| US11212902B2 (en) | 2020-02-25 | 2021-12-28 | Rapiscan Systems, Inc. | Multiplexed drive systems and methods for a multi-emitter X-ray source |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US644029A (en) * | 1899-08-28 | 1900-02-20 | Sherard O Cowper-Coles | Process of electrodeposition of metals. |
| US1506306A (en) * | 1923-10-16 | 1924-08-26 | Kirkaldy Engineering Corp | Anode |
| US2329961A (en) * | 1940-08-12 | 1943-09-21 | Walker William Louis | Apparatus for electrolytic protection of vessels from corrosion |
| NL74768C (en) * | 1950-07-12 | |||
| US2934485A (en) * | 1957-05-13 | 1960-04-26 | Rolland C Sabins | Device and its use for protecting elements against galvanic dissolution |
| US3182007A (en) * | 1958-12-01 | 1965-05-04 | Continental Oil Co | Electrode assembly for the anodic passivation of metals |
| NL288527A (en) * | 1963-02-04 | |||
| US3471395A (en) * | 1966-12-12 | 1969-10-07 | Duriron Co | Anode for cathodic protection |
| US4175021A (en) * | 1978-03-06 | 1979-11-20 | C. E. Equipment Co., Inc. | Apparatus for preventing end effect in anodes |
| US4224126A (en) * | 1979-04-12 | 1980-09-23 | Bidwell Arthur W | Anode assembly for hot water heaters |
-
1981
- 1981-01-13 US US06/224,803 patent/US4420382A/en not_active Expired - Fee Related
- 1981-01-16 CA CA000368658A patent/CA1154719A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4420382A (en) | 1983-12-13 |
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