CA2078616A1 - Cathodic protection anode and method - Google Patents
Cathodic protection anode and methodInfo
- Publication number
- CA2078616A1 CA2078616A1 CA 2078616 CA2078616A CA2078616A1 CA 2078616 A1 CA2078616 A1 CA 2078616A1 CA 2078616 CA2078616 CA 2078616 CA 2078616 A CA2078616 A CA 2078616A CA 2078616 A1 CA2078616 A1 CA 2078616A1
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Abstract
ABSTRACT OF THE DISCLOSURE
An expanded mesh strip of coated valve metal useful for fabricating anode grids for cathodic protection of steel reinforced concrete, tank bottoms, and the like, includes a smooth or uncut lateral edge and is relatively stiff to be packaged and shipped flat for fabrication into such cathodic protection anodes. The strip includes one or more longitudinally extending unexpanded sections to facilitate the tack welding of juxtaposed overlying strips to each other or such strips to conductor ribbons or bars. Several forms of strips are disclosed having various relationships of the expanded and unexpanded sections. The strip and anode formed thereby may be supported in elevated position on a bridge deck to avoid shorting contact with any exposed steel. The strip is easier to fabricate into a precision grid anode and better able to withstand the abuse of a heavy construction site.
An expanded mesh strip of coated valve metal useful for fabricating anode grids for cathodic protection of steel reinforced concrete, tank bottoms, and the like, includes a smooth or uncut lateral edge and is relatively stiff to be packaged and shipped flat for fabrication into such cathodic protection anodes. The strip includes one or more longitudinally extending unexpanded sections to facilitate the tack welding of juxtaposed overlying strips to each other or such strips to conductor ribbons or bars. Several forms of strips are disclosed having various relationships of the expanded and unexpanded sections. The strip and anode formed thereby may be supported in elevated position on a bridge deck to avoid shorting contact with any exposed steel. The strip is easier to fabricate into a precision grid anode and better able to withstand the abuse of a heavy construction site.
Description
2~78~
Title: C~ PRO~C~ION ANODE AN~) ~ETHOD
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Tbis i~lVentjOn relates generally to an allode, and more pc~rticuLarly to a smooth ec3ged valve metal ~esh strip ele~ent whic~ may be fabricated into S cathodic protection anodes for protecting, for exa~ple, storage tank bottoms or steel In steeI reinforced concrete.
The preserlt inven~ion comprises certain impro~ements in fabricated anodes such as shown in copending applic~tion of Michael K. Baach and l;~av~d Kroon, Serial No. û7/6~9,~34 filed ~arch 15, 1991, entitled "Cathodic ProtectionSystem and ~ethod for Above Grolmd Storage ~ank Bottoms" The invention also compnses certain improve~ents in tbe coiled o~ rolled valve metal mesh disclosed in prior ~J.S. Patent No. 4,900,410.
In such prior U.S. patent, rolls or coils of valve metal mesh ~re employed 1~ to fabricate the allode. The coiled or rolled n~esh has several drawbacks, some of w~ich are described in tbe patent. Por example, prior to fabric~tion or fixing the LIlLrolled mesh is preferably stretched longitudinally and/or laterally to improve its flatness and avaid bulges. Such stretching cbanges the dirnensions of the mesb ~nd f.atness is not really acl~ievable. Because of tl~e lack of flatness the ion conductive overlay of polymer modified concrete, whicll m~y be quite thin, may h~e to be applied in se~eral layers. ~e tnesh may be only substantially e~bedded by the first ~ayer. Any protruding sections are ~lattenecl an~/or trimnled before applying the next layer or layers. Tbis makes the overla~ step atirne consuming and expensive project.
~5 ~Iak~'ng tbè above indicated problem ~40rse is the fact that coils or rolls of mesh are usually slit f~om larger rollsl in much the same fashion as a steel coil is slit. ~ider coils are uncoiled, slit ~nd then recoiled. ~c slitting process, even OII steel sheet formf, burrs, but on Inesh, the edges beconle erose, sharp and jagged~ and tend to catch on j~lst ab~ut anything such as workers' clothing, shoes, boots, etc.
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Paving machines for dccks or slabs or spreaders used to form the oYerlay of polynler ~nodifiecl concrete v~te~ use powered rollers alld a~ ers to distIibute smooth ~nd texture the wet concrete. An exan~ple of such machine is the well known Bl~-WELL~ paver sold ~ LL, a divisio~ of ¢MI Co~poration of Canton, South ~)~lcota. I~ the roller o~ auger catches on something it can wrap around the roller or alIger very quic~dy creating a real birds nest, all in a matru of wet concrete. If ~he part ca~l~ht is ~ reticulate anodc grid for a cathodic prote~tion systern, the erltire carefully prepared and fabricated anode may be pulled apart and disinte~rate ~n very short order. ~ rernedial ~easures arc not talcen quickly the entire cast se~ment of deck or paving ~ay need to be replaced.
~t hns been remarked tbat watcbin,~ a concrete placement crew take such action has real e~tertainmellt va~ue because of the sl~eér fren~y inv~lved.
Coiled rnesh str~p5 havmg a curvature ~et are di~icllIt to weld to each other because of the lack of flatness. They won't readily lay flAt over one another.
They usually re4u~re a clamp or at least the top ~nesh strip to be pressed down before a tack or spot veld c~ be made. Evell then a mesh-to-m~sh spot or tac1c weld connection is not as strong as two spot welded non mesh strips ~nother major problem with coiled mesl~ strips used ~s anodes is that the lack of flatness carl creat~ a short b~tween the anode and the metal to b~
protected, thus rendering ~he entire cathodic protection system inoperative. Such shorts discovered after an overlay has been poureà or after a storage tal~ has bcen built abo~e tbe anode can create very e~p~nsive corrective requ~rements.
As indicated in the lloted prior copendin~ application, it is important tbat theallode not touch the bottom of the tanlc which is constructed closely thereover.Tn steel rei~orced concrete bridge deck rep~irs, for exarnple. ~e spalled or broken concrete ;s removed and chipped away before tbe anodc is pl~ced OI1 the deck to thén be embedded in an ion conductive overlay of polyn~er modified concrete which becornes the new sufface of tl~e bridge deck. In the pleparation of the bridge ~eck some of the steel reint`orcing may be exposed so that the allode ~0 mesh must be elevated above the exposed steel. ~or coiled, culve set, mesh strips, this is difficult and any required spacing is problematical. This is ~3 -2 ~
p lr~i~ularly true since during the fal:~ic~tion ~Id subsequent pouring or pavillg yrocess workers will out of necessity be ~alkin~ ver the anode.
It is therefore i~nportant and desirable to provide an ~ode n~esl, strip from which a w~de variet~ of anodes rnay readily be ~bricated whicll does not haYe either thç &urve set or ja~ged edge proble~s of coile~ mesll s-trip. It is also important that the valve ~letal mesh strips be of low cost, easily packagecl ~ndshipped~ and easily handled arld fa~ricated or joirLed at the construction site to fonn a reliable cathodic pro-tection anode.
~ .
In its preferred forrn, the elon~a.ed llat anode strips o~ the presellt invention are formed of annealed titanium strips. The strips bave at least one narrow longitudinal section that is not expanded with the balance of the strip being expanded mesh. The unexpanded section may be at oIle or both edges, or in the m~ddle. The lateral edges of the strip are ei~er tl~e unexpa~lded L longitudinal solid section or a mesh section that is not cut or sheared. In the latte~ configuration the edge presen~s a shallow yet srnooth scallop. Although titanium is preferred, other suitable valve base metals may be used such as aluminu~n, taIltalum, ~ircorlium, niobium, or alloys thereoP The strips after the mesh e~pansion are coated with an ele~trochemically active coating which ~0 prevents passivatio~ of the valve metal s~lrface. The coati~g may for example be a noble metal sucb as platinum or mixed metal oxides.
The unexpanded longitudinal section of the strip may be about 1 crn in width or more so that two overlying and juxtaposed strips m~y readily be tack welded to each other. ~e total strip expanded Inay be ~-12 cm in width, as an ex~uple and the strip is cut into nom~nal un~fortn length~ sudl as 2 meters for stacking, packaging and shippin~ to the anode construction site.
Th~ strip has sufficient~au~e or t~ickness to be able to be stacke~ e boards and sbipped for f~bri~ation and assembly. The une~panded se~rncnts of the strip contribute to ehe handleability and stiffness of ehe s~ips. ~he thickness of tbe strip may ~e from abou~ 0 25 to 2.0 mr~.
~7~fi~ ~
The strip is expanded by ~ormin~ lon~itlldi~ ly exten~ g brickwork s]its of equal le~gtll in ~e ~rea to ~e expanded and thell plllling the st~ip ~ridtllwise to ~orrn a u~form dialnond pattern mesh. Cut or f~achlrçd later~ eclges are avoided.
S The strip in fabrication has sufficient ~latness ~d stiffi:lcss to be readily joined to other strip, and yet caIl readily be bent to go around corners or cut with tin snips. ~Iore innportantly t~e strip can be courlted on to stay where it is supposed to stay in the noImally chaotic and abusive environment of heavy construction.
To the accomplishrnent of the fore,~oing and related ends the invention, then, comprises the features hereinafter fully described and particu~arly pointed out in the claims, the follow~ng description alld the anne~ed drawings setting forth in detail certain illustrative embodiments of the inventioIl, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
Ill said annexed drawings:
Fi~lre 1 is a, schematic illustration of a steel reinforced concrete slab or bridge dec3c wi~h a fal~ric~ted anode in accordance with the present irlvention prior to the application of an overlay;
Pi~ure ~ is a fia,gmentary plan view of a preferred forrn of ~node strip in accordance 4itl~ the present invention;
~i~ure 3 is a sirnikar plan view of another i~orm of anode strip;
Fi~ure 4 is ~ similar view of yet another form of anode strip;
ZS ~i~ure S is a view showin~ the strip of ~i~ure 4 t~ck welded to a traI~sversc conductor ribbon or bar;
Pigure ~ is a view showing the strip of ~igure 3 tacl; welded to such ribbon nr bar;
~igure 7 is a view sim~lar to Figure S but showing the strip/bar conIlection supported on an el~vatin~ shim w~th the aid of a "christInas tree" fastener;
Figure 8 is A similar view but w~th the strip of ~i~ure ~;
2 ~
Figure ~ is a vertieal section through the steel re~nforce(l coI1crete illustrating how the shims and ~asteners suppo~ the anode strip grid above any exposed steel rei~forcing in the concrete;
Fi~ure lO is a view similar lO Figu*e 7 but showing the fastener and 5hirn S offset from the ribbon or bar;
Figure 11 is a 6imil~ i11ustration of an of~set cormection and support ~ith a mesh strip o:P the type seen in Fi~u~e 3;
Pigure 12 is a somewhat enlar~ed horizorltal section t~ken from t~e ~ine 1~-12 of Figure ~ sllowing the fastener in section and the s~im in top plan;
1~ Figure 13 is a top plan vievv of a crossing intersection o~ strips as seen in Figure 4;
Figure 14 is an inte~sectiQr~ of the strips of Fi~ure 3;
~igure 15 is a~ intersection of the strips of Pig~re 2;
~igure 16 is a top pIan view of an anode for a ta~lc bottom, for example ~vhich may be constructed with strips of the present invention:
~igure 17 is a top plan v~ew of a corner which ~ay be &onstructed by flat folding the strip of Pigure 4, the co~ner bein~ supported on a fastener an~l shim;
~igure 18 illustr~tes how arl obtuse an~gle bend is ~ormed;
Figure ~9 ill~strates how an acute angle bend is formed:
~0 Fig~re 20 is a ri~ht an~le corner formed by the strip of Figllre 3; and Figure 21 is a sirnilar corner formed by the strip of ~igure 2.
Nrrs R~fe~rirl~g initially to ~igure 1 there is illustrated a steel reinforced co:~crete slab or deck 30 which is reirlforced by reinforcin~ steel sho~n ~enerally ~5 at 31 and which bas positioned on the top surface thereof a grid ~pe overlay allode shown gen~rally at 3~, fabrieated in accordance with the present invention The grid anode is illustrated before it is bul~ed by tbe ioll conductive overl~y. In the illustration of Figure 1 the grid is formed by positioning ~onductive ribbons Ol bars seen. at ~4 and 35, then placing the mesh strips 36 tra~lsversely thereof E~ch strip is tack or spot welded to the conductor ba~ to forrn a reticulate grid or pattern, such welding not only securing the components of the grid to~e~er but 2 ~3 7 ~
also providin~ a low resistance electric~l connection between each of the CO:t}lpOllelltS, Befole the overl~y is po~red, the ~rid may be electrically connected to rectifier 3g which is connectecl at 39 to the bar 34 a~d at 40 to the reinforc~n~
steel. The connection may also take place after the pouring of the overlay. In S thi~ m~ner a cathodic proteetion current is impressed between the anode grid and the reinforc~ng steel to abate corrosion and the well lalown deleterious effects such ~ corrosion has on steel rei~orced con~et~ b~idges and deck~.
Either ribbons or bars may be utilized as the tran~verse con~uctors i~lustrated in Figure 1 T~e term "~ibbon" simply denotes a bar of ~ ler dimension. J3oth the ribbon and bar have a titamum substrate which m~y h~ve a coating of one of the noble metals or of mixed metal oxides. For both the ribbon and bar, the colnposition of the substrate iç preferably ASTM ~65;
titanium gr~de one or two. The ribbon is preferably 0.25 ~nch in width, 0.0~5 inch in thicl~ess, having a ~,veight of 6 pounds per 500 feet ancl a resistance of 0.042 ohms per foot. ~ anode ribbon with a titanium substrate and a TIR ~000 m~xed n~etal oxide coating, i5 available from a materials protection company of Houston, Texas. The ribbons come i~ 500 ft reels.
The conductor bar may be of the same substrate. The conductor bars or rib~ons are use~ to form the grid pattem and thereby reduce the voltage drop ~0 along the mesh strips. The conductor bars may be preferably 0.5 inch ill width, 0 0~0 inch in thiclcness, have a weight of 10 pou~ds per 250 feet, and have a resistance of 0.013 ohms p~r foot. S~lch conductor bars are avail~le in 250 ft ~oils.
Referring now additionally to ~i~ures ~-4 it will be secn that the mesh ~5 strips 36 may take several fornls. In each form the strip i5 pr~m~r~ly open mesh and includes at least one solid longitudinal section which is of a width to facilitate the t~ck welding of strips either to the~nselves or to the conductor bar or ribbon.
In Fi~ure ~ there is illustrated a mesh strip 40 which includes a ~enter longitudinally extending solid section 41 with raesh sections 42 an~ 43 on both sides.
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The forl~l of strip in ~i~ure 3 in~icated at 45 has one solid longitlldir~al section 46 which forms one lateral ed~e. ~n expancled or mesh sect;on 47 forms the adJacent lateral ed~e.
In Figure 4 there is illustr~ted the ~esh s~rip 3b which is seen in Figure 1. The mcsh strip 36 includes solid lateral borders 4g ~nd 50 with a mesh sectioS1 therebetween.
All t~ree fo~ns of mesh strip may ~se fonned by forr~g r~latively short lorlgitudinal brickwork slits in titar~um metal 5trip. Suçh siits will IlOt be formed in the solid sections 41, 4~, 49 or 50. ~fter ~e slits are formed the stnp is expanded laterally literally by p~ g at the edges to form the open me~h neh~orl;. rn conr~ection with the embodimellts of Figures ~ and 3, care is takenIlOt to fra~ture or cut the lateral edges of the mesh strip seen ~t S~ and 53 in the Fig~re ~ embodiment, and 54 in the ~igure 3 ernbo~iment. Thus even though scalloped in the diamond pattern formed, the lateral edges ~e uncut or unsheared ~nd do not form a jagged ed~c which can catch on work:ers' clothing sueh as gloves, boots, or the like. The embodiments of Figures ~ and 3 form smootb no~jaggecl lateral ed~es even ~ough on the mesh side those cdges are not linear. In the embo~iment of ~i~ure ~ the lateTal ed~es are smooth and linear.
?0 Althou~gh titan~um i9 iIldicated to be the preferred valve metal, ;t w~ll be appreciated that other valve metals may be employed such as aluminum, tantalu~, ~ircor~um or niobium, and alloys thereo After the strip is expanded to the form~ sllown in Pigllres 2-4, it is then coated with an electrochemica~ly active coating wb~ch prevents passivatiotl of the ?~ valve Ihetal surface. The coatin~ may be a mLxed metal oxide coa~ g such as tbat note~ above for ~he titanium ribbon or bar. ~e coating also may be of ~ noble lllet~l. A wide varie~ of electrochemically active coatings Inay be employec~ and reference may be had to prior ~J.S. Patent~ 4,51~,886, or 4,331,528, or U.K.
Pub]ication 896912, published ~ay ~3, ~962, all of which ~how titanium anodes with a va~e~ of mLl~ed me~al oxide coat~ngs OI Iloble metal coatiIIgs.
The mesh strips after being coated are flat ~ld c-lt to len~th for p~ck~ging alld shippi~g, ~ nominal shipping len~th r:lay be on the order of 2 to 4 nleters.
While the dimensions of the mesh st~ips may vary widely, it is important that the strips be flat, have smooth or nonja~ged lateral ed~es, and ~e rel~tively stiff. ~o achieve the latter the thickness of the s~r~p rna~f, for exanlple, be from about 0.25 to 2.0 rnm. The mes~l strip may also vary considerably in ~idth ~d a preferred overall w~dth may be on the order of 6 to 1~ cm, As will be explained, tlle purpose of th~ unexpanded or solid longitudinal sections of the strip is to facilitate tack or 5pot welding of the strips, both to each other a~d to the underlying conductor bar or ribbon. To fa~ilitate this spot weldi~g, the unexpanded or solid sections should be on the order of at least 0.5Clll and preferably on the order of approxlmately 1 cm. Wider sections may be employed.
Referring now to Figure 5 there is illustrated a mesh strip 3~ overlying a 1~ conductor bar or ribbon 34 with the mesh strip secured to the conductor bar or ribbon by two tack ~r spot welds shown at 56 and 57. Aïtbough tack welds are sllowII at both lateral ed~es of the mesh strip 36, it wi~l be appreciated that for fabrication and electrical purposes, only a single tack weld need be employed, In Fi~ure 6 there is illustrated the mesh strip 45 tack welded at 59 to the ~0 conductor bar or rib~on 34. A~ain the snlid unexpanded edge 46 facilitates the tack weldin~ of the mesh strip to the conductor bar or ribbon.
Re,ferr~g now to l:;igure 7 there is illustrated an intersection of a Inesh strip 36 and a conductor bar or ribbon 34, with the intersection and connection bein~ supported in an elevated or spaced condition froln the rein~rced concrete structure. 'rhe connected intersection is supported on a shim showll at 62. The sh~m is bene~th the intersection and the shim, mesh strip an~l conductor bar or ribboll are all anchored to the concrete structure at the location shown by a fastener ~3 which extends throu~h all three. Similarly, in Figure 8 the n~esh strip 40 and the conductor bar or rib~on ~4 ~re interconnected and supported in elevated position by the shim fi5 and fastener 66.
~9~ ~ ~.3 P~
The rcason for s~lpporting tlle grid of the anode in a spaced or ele~at~d ~osition with r~gard to ~e steel reinfo~ced çoncrete struçt~re is s~en more clearly itl Figure 9. In a typical repair or replacement of a ~teel reinforced concrete decl~, the sp~lled or loose con~rete f~olII the corrosioll of the steel rei~orcing bars S is ~emoved providing a relatively ~at yet solid top surface indicated a~ 68. The spalled coxl~rete is usually r~moved with a j~ckham~er or other equ~lly less exacting instru~ent. In the removal process, some of the steel reinforcin~ bar may be left exposed as indicated at 6~ and 70. If the expose~ reinforcing steel contacts the anode grid, a short will occur ma~cing the system inoperative.
As seen additionally in ~i~ure 12 the spacing shims ~5 may be circular clie cut forms of ~ fairly thick plastic rnesh and the fastener 66 simply ext~Ilds throu~h an ope~ing in the mesh. The fasteners ma~ be of the "christmas tree" type pro~ded wit~ fingers indicated at 72 which whell inserted in drilled holes 73 lock the fastener in pl~ce. The shi~ is sirnply placed over the hole, and the fastener is inserted through a hole whiçh may be drilled or punched in the so]id portion of the mesh strip, ~nd the conductor barl the intersection of whiçh is supportedon top of the shim. A washer S~OWIl at 74 nlay be provided under the head of the fasteneI, if desired. Both the fasterler ~d shim are plastic or non-çonductive and may readily be encased in the ion conductive overlay which is formed over ~0 the top of the fabricated grid. The solid portion of the mesh strip may be tacl~
welded to the ribbon or b3r on either side of tbe drilled hole accomlnodatin~ the stem of the ~stener.
Tn ~i~res 10 and 11 there is illustrated an intersection which is supported ~n elevated or space~ colldition by fasteners and shi~s vhich are ~fset from the tack weld interconne~tion of the mesh and collductor bar. ~n Figure 20 the fastener extends through a hole punched in the mesh section 51 (~f the strip with ~he shim nonetheless extencling beneath tlle conductor bar or ribbon 34. II
Fi~ure 11 the mesh strip 45 is tack welded to the b~r or ribbo~ 34 as iudic~ted at 5~ and the shim ~5 extends bene~th the ribbon at the ~ntersectiorl w~th the fastener ~ extendin~ through the expanded mesh section. The dia~nond shape openings in the mesh ~e~tion are of sufficient size tbat the steIn of the f~stener ~10-2 ~ 3 fits through the opening witho~t requiritlg a drilled or punched hole. 'ln any evel1t as seen in Fi~lres 7-1~ tlle el~va~ed or ~paced auchoring of the intelsectioIls uf the mesh strip ~d/or mesh strip and bar enable the grid o~ the allode to be spaced fror~ ally expos~d steel in the structure and the fasteners are of sufficient streIl~th that if someone steps on the mesh ~rid as in Figure 9, there is enou~htensioII in the ilat ~nd stiff mesh strip to cau~e it to spri~g back to its spaced or elevated position.
It will be appreciated that the Inesh strips may be joitled to each oLher as easily as they are joine~ to the ribbons o~ conductor bars. They may also be supported in the elevated or spac~d condition seen ~n Figure ~ at such intersections by the employment of the shims a~d fasteners. Figure 13 illustrates a right angle intersection between two rnesh strips 36 of the ype seen in Figure4. The intersection of the solid bo~ders may each be tack welded as ~een at 80, 81, 82 and 83. It will be appreciated that normally four such welds will not be reg,uired. The fabricator however has a number of options in making the connectiou and intersectio~.
In Fi~ure 14 the~e is i~lustrated a31 intersection of t,wo mesh strips 45 of thetype seen in Figure 3. A sirl~le tac~ weld 8S is employed join~ng the two solid sections of the mesh strips. ~n Figure 15 there is illustrated a ri&ht ~ngle intersection of two mesh strips 40 of the type seen in Figure 10 and again a single ta~k weld is employed at 87 join~ng the respective solid longitlldinal sections of the overlying mesh strips. It will be appreciated that the intersection need not be a right angle intersection and that the layout or fabrication of the ~rid may call for other angular connection~. ~t will also be appreciated that the strip may betack welded end-to-end to form the cut to length sections into much longer sections, a~ain using the solid longitudinal sections overlying each oth~r to facilitate the tack weld~n~.
Fi~ure 16 illustrates ~ fabric~ted allode ~rid of the type which m~y be used to protect new or reconstructed circular tank bottoIns such ~s described ~n -the~0 aforenoted copending application Se~ial No. 66g,934. The anode grid of Fi~lre 16 may be constructed on a layer of comp~ted sand and is designed to protect 2 ~
a tank bottom which would be constructed rnostly above the anode grid. ~'he circlllar tank 90 util~zes an anode grid shown generally at gl which is formed of chordal conductor bar 9~, diametral conclucto~ bar ~3, and symmetrically disposed chor~al conductor b~r 94. Extendi~g no~nal to s~ch conductor bars Oll S approximately 4-foot centers are anode ~esh strips ~6 in ~ccord~ce with the present invention. ~n ~ddition to the Inajor conductor bars 9~, ~3 a~d ~4, relatively short curre~t distribut~r bars may ~e prov~ded ~or the shortest mesh strips as illdicated at 98, 99, 100 and lO1. Power lead co~ections from the r~ctifier are provided at 103, 104, 105 and 10~ while the trian~ular symbols indicate the locations of reference electrodes as seen at 108 and 10~. ReferenceIhay be had to the noted copendin~ applicatiorl for a wide variety OI grids ~vhich may be constructed for the protection of tank bottoms ~tili~ing the mesh strip of tlle present invention. ~rid type ano~es co~stnlcted urlder tank bottoms ar~
subject to the same type of chaotic and abusive environment as ~rid ~pe anodes which are to be encased on a concrete stn~ct-ure or deck with aIl overlay.
~Ioreover, both requi~e care and precisior~ in construction in or~er to functionproperly.
~eferring now to Figures 17~0 it will be seen that the mesh strips of the present invention may be flat folded at certa~n angles to create bends, either at a right an~le, or at the acute or obtuse angles illustrated. In Fi~e 17 a mesll strip of the type seen in Figure 4 is bent to a flat fold at a 45 an~le to form the right a4gle ~end sl~ow~ he interio~ crotch of the bend may be s~pported on a spaci~g shim indicated at 65 and anchored in place with fastener ~. ~ Figure 18 an obtu~e angle bend is for~ed. To keep the mesh ~trip in tlle flat stiff ~5 condition at the bend the two solid edges m~y be tack welded together as il~dicated at 112, In Fi~ure 1~ ~ acute angle bend is formed and ag~in the opposite solid edges may be tack welded to~ether as seen at 114. In Fi~e 20 a ~esh ~trip of the type ~een in Figure 3 is flat folded to forrn a right ~ngle bend. Figure ~1 illustrates a nght an~le bend ~th a mesh s~ip of the l;ype see~ in ~igure ~. ~3oth are simply folded a~ a 45Q angle to create the right angle bend. A flat fold w~th ~ ~ 7 ~
the mesl1 strip of th~ pres~nt inventioll ~ay readily be acbieved, If necessaly a pair of pliers may be employ~d to form the crease. Also in the embodiments of ~'igures 20 and 21 a tack weld may be formed at 114 or 116 to ma~n~aill the meshstrip in its ~at ~olded conditioll.
S It can now be seen that the mesh strip af t~e present ~nvention has sufficient flatlless and stiffness readily to ~e jo~lled to olher str~p, and yet c~
readily be bent to go around corners or to be cut v.~t:~ tin sn~ps and rejoined at any ~ngle. More importantly the strip can be counted on ~o stay where it is supposed to stay in the no~nally chaotic a~d abnsive environment of heavy coIls~ction.
~Ithou,~h the iIIvention has been shown and ~escribed wi~ respect to certain preferred embod~ments, it is obvious tbat equivalent altera~ions alld modifications ~Ivill occur to others sl~lled in tlle art upon the reading and understandin~ of t~i~ specification. ~e p~esent invention iilc~udes all such e~quivalent alterations and modifications, and is lir~ited only by the scope of the claims,
Title: C~ PRO~C~ION ANODE AN~) ~ETHOD
~LQ~
Tbis i~lVentjOn relates generally to an allode, and more pc~rticuLarly to a smooth ec3ged valve metal ~esh strip ele~ent whic~ may be fabricated into S cathodic protection anodes for protecting, for exa~ple, storage tank bottoms or steel In steeI reinforced concrete.
The preserlt inven~ion comprises certain impro~ements in fabricated anodes such as shown in copending applic~tion of Michael K. Baach and l;~av~d Kroon, Serial No. û7/6~9,~34 filed ~arch 15, 1991, entitled "Cathodic ProtectionSystem and ~ethod for Above Grolmd Storage ~ank Bottoms" The invention also compnses certain improve~ents in tbe coiled o~ rolled valve metal mesh disclosed in prior ~J.S. Patent No. 4,900,410.
In such prior U.S. patent, rolls or coils of valve metal mesh ~re employed 1~ to fabricate the allode. The coiled or rolled n~esh has several drawbacks, some of w~ich are described in tbe patent. Por example, prior to fabric~tion or fixing the LIlLrolled mesh is preferably stretched longitudinally and/or laterally to improve its flatness and avaid bulges. Such stretching cbanges the dirnensions of the mesb ~nd f.atness is not really acl~ievable. Because of tl~e lack of flatness the ion conductive overlay of polymer modified concrete, whicll m~y be quite thin, may h~e to be applied in se~eral layers. ~e tnesh may be only substantially e~bedded by the first ~ayer. Any protruding sections are ~lattenecl an~/or trimnled before applying the next layer or layers. Tbis makes the overla~ step atirne consuming and expensive project.
~5 ~Iak~'ng tbè above indicated problem ~40rse is the fact that coils or rolls of mesh are usually slit f~om larger rollsl in much the same fashion as a steel coil is slit. ~ider coils are uncoiled, slit ~nd then recoiled. ~c slitting process, even OII steel sheet formf, burrs, but on Inesh, the edges beconle erose, sharp and jagged~ and tend to catch on j~lst ab~ut anything such as workers' clothing, shoes, boots, etc.
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Paving machines for dccks or slabs or spreaders used to form the oYerlay of polynler ~nodifiecl concrete v~te~ use powered rollers alld a~ ers to distIibute smooth ~nd texture the wet concrete. An exan~ple of such machine is the well known Bl~-WELL~ paver sold ~ LL, a divisio~ of ¢MI Co~poration of Canton, South ~)~lcota. I~ the roller o~ auger catches on something it can wrap around the roller or alIger very quic~dy creating a real birds nest, all in a matru of wet concrete. If ~he part ca~l~ht is ~ reticulate anodc grid for a cathodic prote~tion systern, the erltire carefully prepared and fabricated anode may be pulled apart and disinte~rate ~n very short order. ~ rernedial ~easures arc not talcen quickly the entire cast se~ment of deck or paving ~ay need to be replaced.
~t hns been remarked tbat watcbin,~ a concrete placement crew take such action has real e~tertainmellt va~ue because of the sl~eér fren~y inv~lved.
Coiled rnesh str~p5 havmg a curvature ~et are di~icllIt to weld to each other because of the lack of flatness. They won't readily lay flAt over one another.
They usually re4u~re a clamp or at least the top ~nesh strip to be pressed down before a tack or spot veld c~ be made. Evell then a mesh-to-m~sh spot or tac1c weld connection is not as strong as two spot welded non mesh strips ~nother major problem with coiled mesl~ strips used ~s anodes is that the lack of flatness carl creat~ a short b~tween the anode and the metal to b~
protected, thus rendering ~he entire cathodic protection system inoperative. Such shorts discovered after an overlay has been poureà or after a storage tal~ has bcen built abo~e tbe anode can create very e~p~nsive corrective requ~rements.
As indicated in the lloted prior copendin~ application, it is important tbat theallode not touch the bottom of the tanlc which is constructed closely thereover.Tn steel rei~orced concrete bridge deck rep~irs, for exarnple. ~e spalled or broken concrete ;s removed and chipped away before tbe anodc is pl~ced OI1 the deck to thén be embedded in an ion conductive overlay of polyn~er modified concrete which becornes the new sufface of tl~e bridge deck. In the pleparation of the bridge ~eck some of the steel reint`orcing may be exposed so that the allode ~0 mesh must be elevated above the exposed steel. ~or coiled, culve set, mesh strips, this is difficult and any required spacing is problematical. This is ~3 -2 ~
p lr~i~ularly true since during the fal:~ic~tion ~Id subsequent pouring or pavillg yrocess workers will out of necessity be ~alkin~ ver the anode.
It is therefore i~nportant and desirable to provide an ~ode n~esl, strip from which a w~de variet~ of anodes rnay readily be ~bricated whicll does not haYe either thç &urve set or ja~ged edge proble~s of coile~ mesll s-trip. It is also important that the valve ~letal mesh strips be of low cost, easily packagecl ~ndshipped~ and easily handled arld fa~ricated or joirLed at the construction site to fonn a reliable cathodic pro-tection anode.
~ .
In its preferred forrn, the elon~a.ed llat anode strips o~ the presellt invention are formed of annealed titanium strips. The strips bave at least one narrow longitudinal section that is not expanded with the balance of the strip being expanded mesh. The unexpanded section may be at oIle or both edges, or in the m~ddle. The lateral edges of the strip are ei~er tl~e unexpa~lded L longitudinal solid section or a mesh section that is not cut or sheared. In the latte~ configuration the edge presen~s a shallow yet srnooth scallop. Although titanium is preferred, other suitable valve base metals may be used such as aluminu~n, taIltalum, ~ircorlium, niobium, or alloys thereoP The strips after the mesh e~pansion are coated with an ele~trochemically active coating which ~0 prevents passivatio~ of the valve metal s~lrface. The coati~g may for example be a noble metal sucb as platinum or mixed metal oxides.
The unexpanded longitudinal section of the strip may be about 1 crn in width or more so that two overlying and juxtaposed strips m~y readily be tack welded to each other. ~e total strip expanded Inay be ~-12 cm in width, as an ex~uple and the strip is cut into nom~nal un~fortn length~ sudl as 2 meters for stacking, packaging and shippin~ to the anode construction site.
Th~ strip has sufficient~au~e or t~ickness to be able to be stacke~ e boards and sbipped for f~bri~ation and assembly. The une~panded se~rncnts of the strip contribute to ehe handleability and stiffness of ehe s~ips. ~he thickness of tbe strip may ~e from abou~ 0 25 to 2.0 mr~.
~7~fi~ ~
The strip is expanded by ~ormin~ lon~itlldi~ ly exten~ g brickwork s]its of equal le~gtll in ~e ~rea to ~e expanded and thell plllling the st~ip ~ridtllwise to ~orrn a u~form dialnond pattern mesh. Cut or f~achlrçd later~ eclges are avoided.
S The strip in fabrication has sufficient ~latness ~d stiffi:lcss to be readily joined to other strip, and yet caIl readily be bent to go around corners or cut with tin snips. ~Iore innportantly t~e strip can be courlted on to stay where it is supposed to stay in the noImally chaotic and abusive environment of heavy construction.
To the accomplishrnent of the fore,~oing and related ends the invention, then, comprises the features hereinafter fully described and particu~arly pointed out in the claims, the follow~ng description alld the anne~ed drawings setting forth in detail certain illustrative embodiments of the inventioIl, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
Ill said annexed drawings:
Fi~lre 1 is a, schematic illustration of a steel reinforced concrete slab or bridge dec3c wi~h a fal~ric~ted anode in accordance with the present irlvention prior to the application of an overlay;
Pi~ure ~ is a fia,gmentary plan view of a preferred forrn of ~node strip in accordance 4itl~ the present invention;
~i~ure 3 is a sirnikar plan view of another i~orm of anode strip;
Fi~ure 4 is ~ similar view of yet another form of anode strip;
ZS ~i~ure S is a view showin~ the strip of ~i~ure 4 t~ck welded to a traI~sversc conductor ribbon or bar;
Pigure ~ is a view showing the strip of ~igure 3 tacl; welded to such ribbon nr bar;
~igure 7 is a view sim~lar to Figure S but showing the strip/bar conIlection supported on an el~vatin~ shim w~th the aid of a "christInas tree" fastener;
Figure 8 is A similar view but w~th the strip of ~i~ure ~;
2 ~
Figure ~ is a vertieal section through the steel re~nforce(l coI1crete illustrating how the shims and ~asteners suppo~ the anode strip grid above any exposed steel rei~forcing in the concrete;
Fi~ure lO is a view similar lO Figu*e 7 but showing the fastener and 5hirn S offset from the ribbon or bar;
Figure 11 is a 6imil~ i11ustration of an of~set cormection and support ~ith a mesh strip o:P the type seen in Fi~u~e 3;
Pigure 12 is a somewhat enlar~ed horizorltal section t~ken from t~e ~ine 1~-12 of Figure ~ sllowing the fastener in section and the s~im in top plan;
1~ Figure 13 is a top plan vievv of a crossing intersection o~ strips as seen in Figure 4;
Figure 14 is an inte~sectiQr~ of the strips of Fi~ure 3;
~igure 15 is a~ intersection of the strips of Pig~re 2;
~igure 16 is a top pIan view of an anode for a ta~lc bottom, for example ~vhich may be constructed with strips of the present invention:
~igure 17 is a top plan v~ew of a corner which ~ay be &onstructed by flat folding the strip of Pigure 4, the co~ner bein~ supported on a fastener an~l shim;
~igure 18 illustr~tes how arl obtuse an~gle bend is ~ormed;
Figure ~9 ill~strates how an acute angle bend is formed:
~0 Fig~re 20 is a ri~ht an~le corner formed by the strip of Figllre 3; and Figure 21 is a sirnilar corner formed by the strip of ~igure 2.
Nrrs R~fe~rirl~g initially to ~igure 1 there is illustrated a steel reinforced co:~crete slab or deck 30 which is reirlforced by reinforcin~ steel sho~n ~enerally ~5 at 31 and which bas positioned on the top surface thereof a grid ~pe overlay allode shown gen~rally at 3~, fabrieated in accordance with the present invention The grid anode is illustrated before it is bul~ed by tbe ioll conductive overl~y. In the illustration of Figure 1 the grid is formed by positioning ~onductive ribbons Ol bars seen. at ~4 and 35, then placing the mesh strips 36 tra~lsversely thereof E~ch strip is tack or spot welded to the conductor ba~ to forrn a reticulate grid or pattern, such welding not only securing the components of the grid to~e~er but 2 ~3 7 ~
also providin~ a low resistance electric~l connection between each of the CO:t}lpOllelltS, Befole the overl~y is po~red, the ~rid may be electrically connected to rectifier 3g which is connectecl at 39 to the bar 34 a~d at 40 to the reinforc~n~
steel. The connection may also take place after the pouring of the overlay. In S thi~ m~ner a cathodic proteetion current is impressed between the anode grid and the reinforc~ng steel to abate corrosion and the well lalown deleterious effects such ~ corrosion has on steel rei~orced con~et~ b~idges and deck~.
Either ribbons or bars may be utilized as the tran~verse con~uctors i~lustrated in Figure 1 T~e term "~ibbon" simply denotes a bar of ~ ler dimension. J3oth the ribbon and bar have a titamum substrate which m~y h~ve a coating of one of the noble metals or of mixed metal oxides. For both the ribbon and bar, the colnposition of the substrate iç preferably ASTM ~65;
titanium gr~de one or two. The ribbon is preferably 0.25 ~nch in width, 0.0~5 inch in thicl~ess, having a ~,veight of 6 pounds per 500 feet ancl a resistance of 0.042 ohms per foot. ~ anode ribbon with a titanium substrate and a TIR ~000 m~xed n~etal oxide coating, i5 available from a materials protection company of Houston, Texas. The ribbons come i~ 500 ft reels.
The conductor bar may be of the same substrate. The conductor bars or rib~ons are use~ to form the grid pattem and thereby reduce the voltage drop ~0 along the mesh strips. The conductor bars may be preferably 0.5 inch ill width, 0 0~0 inch in thiclcness, have a weight of 10 pou~ds per 250 feet, and have a resistance of 0.013 ohms p~r foot. S~lch conductor bars are avail~le in 250 ft ~oils.
Referring now additionally to ~i~ures ~-4 it will be secn that the mesh ~5 strips 36 may take several fornls. In each form the strip i5 pr~m~r~ly open mesh and includes at least one solid longitudinal section which is of a width to facilitate the t~ck welding of strips either to the~nselves or to the conductor bar or ribbon.
In Fi~ure ~ there is illustrated a mesh strip 40 which includes a ~enter longitudinally extending solid section 41 with raesh sections 42 an~ 43 on both sides.
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The forl~l of strip in ~i~ure 3 in~icated at 45 has one solid longitlldir~al section 46 which forms one lateral ed~e. ~n expancled or mesh sect;on 47 forms the adJacent lateral ed~e.
In Figure 4 there is illustr~ted the ~esh s~rip 3b which is seen in Figure 1. The mcsh strip 36 includes solid lateral borders 4g ~nd 50 with a mesh sectioS1 therebetween.
All t~ree fo~ns of mesh strip may ~se fonned by forr~g r~latively short lorlgitudinal brickwork slits in titar~um metal 5trip. Suçh siits will IlOt be formed in the solid sections 41, 4~, 49 or 50. ~fter ~e slits are formed the stnp is expanded laterally literally by p~ g at the edges to form the open me~h neh~orl;. rn conr~ection with the embodimellts of Figures ~ and 3, care is takenIlOt to fra~ture or cut the lateral edges of the mesh strip seen ~t S~ and 53 in the Fig~re ~ embodiment, and 54 in the ~igure 3 ernbo~iment. Thus even though scalloped in the diamond pattern formed, the lateral edges ~e uncut or unsheared ~nd do not form a jagged ed~c which can catch on work:ers' clothing sueh as gloves, boots, or the like. The embodiments of Figures ~ and 3 form smootb no~jaggecl lateral ed~es even ~ough on the mesh side those cdges are not linear. In the embo~iment of ~i~ure ~ the lateTal ed~es are smooth and linear.
?0 Althou~gh titan~um i9 iIldicated to be the preferred valve metal, ;t w~ll be appreciated that other valve metals may be employed such as aluminum, tantalu~, ~ircor~um or niobium, and alloys thereo After the strip is expanded to the form~ sllown in Pigllres 2-4, it is then coated with an electrochemica~ly active coating wb~ch prevents passivatiotl of the ?~ valve Ihetal surface. The coatin~ may be a mLxed metal oxide coa~ g such as tbat note~ above for ~he titanium ribbon or bar. ~e coating also may be of ~ noble lllet~l. A wide varie~ of electrochemically active coatings Inay be employec~ and reference may be had to prior ~J.S. Patent~ 4,51~,886, or 4,331,528, or U.K.
Pub]ication 896912, published ~ay ~3, ~962, all of which ~how titanium anodes with a va~e~ of mLl~ed me~al oxide coat~ngs OI Iloble metal coatiIIgs.
The mesh strips after being coated are flat ~ld c-lt to len~th for p~ck~ging alld shippi~g, ~ nominal shipping len~th r:lay be on the order of 2 to 4 nleters.
While the dimensions of the mesh st~ips may vary widely, it is important that the strips be flat, have smooth or nonja~ged lateral ed~es, and ~e rel~tively stiff. ~o achieve the latter the thickness of the s~r~p rna~f, for exanlple, be from about 0.25 to 2.0 rnm. The mes~l strip may also vary considerably in ~idth ~d a preferred overall w~dth may be on the order of 6 to 1~ cm, As will be explained, tlle purpose of th~ unexpanded or solid longitudinal sections of the strip is to facilitate tack or 5pot welding of the strips, both to each other a~d to the underlying conductor bar or ribbon. To fa~ilitate this spot weldi~g, the unexpanded or solid sections should be on the order of at least 0.5Clll and preferably on the order of approxlmately 1 cm. Wider sections may be employed.
Referring now to Figure 5 there is illustrated a mesh strip 3~ overlying a 1~ conductor bar or ribbon 34 with the mesh strip secured to the conductor bar or ribbon by two tack ~r spot welds shown at 56 and 57. Aïtbough tack welds are sllowII at both lateral ed~es of the mesh strip 36, it wi~l be appreciated that for fabrication and electrical purposes, only a single tack weld need be employed, In Fi~ure 6 there is illustrated the mesh strip 45 tack welded at 59 to the ~0 conductor bar or rib~on 34. A~ain the snlid unexpanded edge 46 facilitates the tack weldin~ of the mesh strip to the conductor bar or ribbon.
Re,ferr~g now to l:;igure 7 there is illustrated an intersection of a Inesh strip 36 and a conductor bar or ribbon 34, with the intersection and connection bein~ supported in an elevated or spaced condition froln the rein~rced concrete structure. 'rhe connected intersection is supported on a shim showll at 62. The sh~m is bene~th the intersection and the shim, mesh strip an~l conductor bar or ribboll are all anchored to the concrete structure at the location shown by a fastener ~3 which extends throu~h all three. Similarly, in Figure 8 the n~esh strip 40 and the conductor bar or rib~on ~4 ~re interconnected and supported in elevated position by the shim fi5 and fastener 66.
~9~ ~ ~.3 P~
The rcason for s~lpporting tlle grid of the anode in a spaced or ele~at~d ~osition with r~gard to ~e steel reinfo~ced çoncrete struçt~re is s~en more clearly itl Figure 9. In a typical repair or replacement of a ~teel reinforced concrete decl~, the sp~lled or loose con~rete f~olII the corrosioll of the steel rei~orcing bars S is ~emoved providing a relatively ~at yet solid top surface indicated a~ 68. The spalled coxl~rete is usually r~moved with a j~ckham~er or other equ~lly less exacting instru~ent. In the removal process, some of the steel reinforcin~ bar may be left exposed as indicated at 6~ and 70. If the expose~ reinforcing steel contacts the anode grid, a short will occur ma~cing the system inoperative.
As seen additionally in ~i~ure 12 the spacing shims ~5 may be circular clie cut forms of ~ fairly thick plastic rnesh and the fastener 66 simply ext~Ilds throu~h an ope~ing in the mesh. The fasteners ma~ be of the "christmas tree" type pro~ded wit~ fingers indicated at 72 which whell inserted in drilled holes 73 lock the fastener in pl~ce. The shi~ is sirnply placed over the hole, and the fastener is inserted through a hole whiçh may be drilled or punched in the so]id portion of the mesh strip, ~nd the conductor barl the intersection of whiçh is supportedon top of the shim. A washer S~OWIl at 74 nlay be provided under the head of the fasteneI, if desired. Both the fasterler ~d shim are plastic or non-çonductive and may readily be encased in the ion conductive overlay which is formed over ~0 the top of the fabricated grid. The solid portion of the mesh strip may be tacl~
welded to the ribbon or b3r on either side of tbe drilled hole accomlnodatin~ the stem of the ~stener.
Tn ~i~res 10 and 11 there is illustrated an intersection which is supported ~n elevated or space~ colldition by fasteners and shi~s vhich are ~fset from the tack weld interconne~tion of the mesh and collductor bar. ~n Figure 20 the fastener extends through a hole punched in the mesh section 51 (~f the strip with ~he shim nonetheless extencling beneath tlle conductor bar or ribbon 34. II
Fi~ure 11 the mesh strip 45 is tack welded to the b~r or ribbo~ 34 as iudic~ted at 5~ and the shim ~5 extends bene~th the ribbon at the ~ntersectiorl w~th the fastener ~ extendin~ through the expanded mesh section. The dia~nond shape openings in the mesh ~e~tion are of sufficient size tbat the steIn of the f~stener ~10-2 ~ 3 fits through the opening witho~t requiritlg a drilled or punched hole. 'ln any evel1t as seen in Fi~lres 7-1~ tlle el~va~ed or ~paced auchoring of the intelsectioIls uf the mesh strip ~d/or mesh strip and bar enable the grid o~ the allode to be spaced fror~ ally expos~d steel in the structure and the fasteners are of sufficient streIl~th that if someone steps on the mesh ~rid as in Figure 9, there is enou~htensioII in the ilat ~nd stiff mesh strip to cau~e it to spri~g back to its spaced or elevated position.
It will be appreciated that the Inesh strips may be joitled to each oLher as easily as they are joine~ to the ribbons o~ conductor bars. They may also be supported in the elevated or spac~d condition seen ~n Figure ~ at such intersections by the employment of the shims a~d fasteners. Figure 13 illustrates a right angle intersection between two rnesh strips 36 of the ype seen in Figure4. The intersection of the solid bo~ders may each be tack welded as ~een at 80, 81, 82 and 83. It will be appreciated that normally four such welds will not be reg,uired. The fabricator however has a number of options in making the connectiou and intersectio~.
In Fi~ure 14 the~e is i~lustrated a31 intersection of t,wo mesh strips 45 of thetype seen in Figure 3. A sirl~le tac~ weld 8S is employed join~ng the two solid sections of the mesh strips. ~n Figure 15 there is illustrated a ri&ht ~ngle intersection of two mesh strips 40 of the type seen in Figure 10 and again a single ta~k weld is employed at 87 join~ng the respective solid longitlldinal sections of the overlying mesh strips. It will be appreciated that the intersection need not be a right angle intersection and that the layout or fabrication of the ~rid may call for other angular connection~. ~t will also be appreciated that the strip may betack welded end-to-end to form the cut to length sections into much longer sections, a~ain using the solid longitudinal sections overlying each oth~r to facilitate the tack weld~n~.
Fi~ure 16 illustrates ~ fabric~ted allode ~rid of the type which m~y be used to protect new or reconstructed circular tank bottoIns such ~s described ~n -the~0 aforenoted copending application Se~ial No. 66g,934. The anode grid of Fi~lre 16 may be constructed on a layer of comp~ted sand and is designed to protect 2 ~
a tank bottom which would be constructed rnostly above the anode grid. ~'he circlllar tank 90 util~zes an anode grid shown generally at gl which is formed of chordal conductor bar 9~, diametral conclucto~ bar ~3, and symmetrically disposed chor~al conductor b~r 94. Extendi~g no~nal to s~ch conductor bars Oll S approximately 4-foot centers are anode ~esh strips ~6 in ~ccord~ce with the present invention. ~n ~ddition to the Inajor conductor bars 9~, ~3 a~d ~4, relatively short curre~t distribut~r bars may ~e prov~ded ~or the shortest mesh strips as illdicated at 98, 99, 100 and lO1. Power lead co~ections from the r~ctifier are provided at 103, 104, 105 and 10~ while the trian~ular symbols indicate the locations of reference electrodes as seen at 108 and 10~. ReferenceIhay be had to the noted copendin~ applicatiorl for a wide variety OI grids ~vhich may be constructed for the protection of tank bottoms ~tili~ing the mesh strip of tlle present invention. ~rid type ano~es co~stnlcted urlder tank bottoms ar~
subject to the same type of chaotic and abusive environment as ~rid ~pe anodes which are to be encased on a concrete stn~ct-ure or deck with aIl overlay.
~Ioreover, both requi~e care and precisior~ in construction in or~er to functionproperly.
~eferring now to Figures 17~0 it will be seen that the mesh strips of the present invention may be flat folded at certa~n angles to create bends, either at a right an~le, or at the acute or obtuse angles illustrated. In Fi~e 17 a mesll strip of the type seen in Figure 4 is bent to a flat fold at a 45 an~le to form the right a4gle ~end sl~ow~ he interio~ crotch of the bend may be s~pported on a spaci~g shim indicated at 65 and anchored in place with fastener ~. ~ Figure 18 an obtu~e angle bend is for~ed. To keep the mesh ~trip in tlle flat stiff ~5 condition at the bend the two solid edges m~y be tack welded together as il~dicated at 112, In Fi~ure 1~ ~ acute angle bend is formed and ag~in the opposite solid edges may be tack welded to~ether as seen at 114. In Fi~e 20 a ~esh ~trip of the type ~een in Figure 3 is flat folded to forrn a right ~ngle bend. Figure ~1 illustrates a nght an~le bend ~th a mesh s~ip of the l;ype see~ in ~igure ~. ~3oth are simply folded a~ a 45Q angle to create the right angle bend. A flat fold w~th ~ ~ 7 ~
the mesl1 strip of th~ pres~nt inventioll ~ay readily be acbieved, If necessaly a pair of pliers may be employ~d to form the crease. Also in the embodiments of ~'igures 20 and 21 a tack weld may be formed at 114 or 116 to ma~n~aill the meshstrip in its ~at ~olded conditioll.
S It can now be seen that the mesh strip af t~e present ~nvention has sufficient flatlless and stiffness readily to ~e jo~lled to olher str~p, and yet c~
readily be bent to go around corners or to be cut v.~t:~ tin sn~ps and rejoined at any ~ngle. More importantly the strip can be counted on ~o stay where it is supposed to stay in the no~nally chaotic a~d abnsive environment of heavy coIls~ction.
~Ithou,~h the iIIvention has been shown and ~escribed wi~ respect to certain preferred embod~ments, it is obvious tbat equivalent altera~ions alld modifications ~Ivill occur to others sl~lled in tlle art upon the reading and understandin~ of t~i~ specification. ~e p~esent invention iilc~udes all such e~quivalent alterations and modifications, and is lir~ited only by the scope of the claims,
Claims (42)
1. An anode strip for cathodic protection anodes comprising a relatively stiff strip of coated valve metal, said strip having at least one continuous longitudinally extending solid section of sufficient width for spot welding, and the balance of the strip being an open reticulate area.
2. A strip as set forth in claim 1 wherein said solid section is in the center of the strip.
3. A strip as set forth in claim 1 wherein said solid section is at at least one lateral edge.
4. A strip as set forth in claim 1 wherein said solid section is at both lateral edges.
5. A strip as set forth in claim 1 wherein the open reticulate area is in the form of a diamond mesh.
6. A strip as set forth in claim 1 wherein the lateral edges of the open reticulate area are not sheared thereby avoiding a jagged edge.
7. A strip as set forth in claim 1 wherein said strip is flat and unrolled.
8. A strip as set forth in claim 1 wherein said strip is cut to length, stacked, packaged and shipped to a construction site, all while in said flat condition.
9. A strip as set forth in claim 1 wherein said valve metal is selected from the group of titanium, aluminum, tantalum, zirconium, niobium or alloys thereof.
10. A coated valve metal elongated element for use in constructing cathodic protection anodes, said strip element comprising continuous lateral edges with an expanded open mesh between such edges, said edges being unsheared after expansion.
11. An element as set forth in claim 10 including at least one continuous longitudinally extending solid section of sufficient width for spot welding.
12. An element as set forth in claim 11 wherein said solid section is in the center of the strip.
13. An element as set forth in claim 11 wherein said solid section is at at least one lateral edge.
14. An element as set forth in claim 11 wherein said solid section is at both lateral edges.
15. An element as set forth m claim 10 wherein said open mesh is in the form of a reticulate diamond pattern.
16. An element as set forth in claim 15 wherein each diamond shape opening of the mesh includes a long axis which extends longitudinally of the element.
17. An element as set forth in claim 10 wherein the metal is selected from the group of titanium, aluminum, tantalum, zirconium, niobium, or alloys thereof.
18. An element as set forth in claim 17 wherein the element is titanium.
19. An element as set forth in claim 17 wherein the metal element includes an electrochemically active coating.
20. An element as set forth in claim 19 wherein the coating is of a metal from the platinum family group.
21. An element as set forth in claim 10 wherein the coating is a mixed metal oxide coating.
22. An element as set forth in claim 10 wherein said element is flat and unrolled.
23. An element as set forth in claim 22 wherein said element is cut to length, stacked, packaged and shipped to a construction site all while in said flat condition.
24. An element as set forth in claim 11 wherein said solid section has a width of at least 0.5 cm.
25. An element as set forth in claim 24 wherein said element has an overall width of at least 6 cm.
26. An element as set forth in claim 25 wherein said element has an overall width of from about 6 to about 12 cm.
27. A cathodic protection system comprising an anode, said anode being formed by a pattern of valve metal current distribution strips, each strip comprising non-jagged lateral edges with an open mesh therebetween.
28. A system as set forth in claim 27 wherein each strip includes a longitudinally extending solid section of a width to facilitate spot welding.
29. A system as set forth in claim 28 wherein said strips are welded to current distribution bars or ribbons.
30. A system as set forth in claim 28 wherein said strips are welded to each other.
31. A system as set forth in claim 27 wherein said cathodic protection system is for a steel reinforced concrete structure, and means to space the anode from the structure before encasing the anode in an ion conductive overlay to avoid shorting contact with any steel in such structure.
32. A system as set forth in claim 31 wherein said means to space comprises a non-conductive fastener and non-conductive spacing shim.
33. A system as set forth in claim 32 wherein said shim is a section of plastic mesh.
34. A method of installing an impressed current anode on a steel reinforced concrete structure comprising the steps of:
locating and positioning electrical insulating shims on the concrete structure, bridging such shims with flat relatively stiff valve metal current mesh distributor strips, electrically interconnecting such strips to form a current distributor network spaced from the concrete structure by the shims, and embedding the network in an ion-conducting overlay.
locating and positioning electrical insulating shims on the concrete structure, bridging such shims with flat relatively stiff valve metal current mesh distributor strips, electrically interconnecting such strips to form a current distributor network spaced from the concrete structure by the shims, and embedding the network in an ion-conducting overlay.
35. A method as set forth in claim 34 wherein such strip includes non-jagged lateral borders and at least one solid non-mesh longitudinal section, and said network being formed by electrically connecting said strips at such solid sections.
36. A method as set forth in claim 34 wherein such sections are sufficiently wide to facilitate spot welding at such solid section.
37. A method as set forth in claim 34 wherein said strips are fastened to the concrete through such shims.
38. A method as set forth in claim 34 wherein said strips are anchored at such shims to resist deflection intermediate the shims to enable the strip to spring back to a position spaced from the concrete structure upon deflection.
39. A method as set forth in claim 34 wherein said mesh distributor strips are shipped flat and tack welded to each other or to conductor bar to construct such anode.
40. A method of forming a cathodic protection anode comprising the steps of positioning at least one elongated conductor bar, positioning and securing to said conductor bar one or more current distributor strips transversely of said conductor bar, and electrically securing the bar and strip, each strip having continuous lateral, non-jagged edges and an open reticulate area therebetween.
41. A method as set forth in claim 40 wherein each strip includes at least one longitudinal section which is solid, said section being of a width to facilitate tack welding.
42. A method as set forth in claim 41 including the step of forming a grid by tack welding such strips to each other or to said conductor bar at such solid longitudinal sections.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US76317991A | 1991-09-20 | 1991-09-20 | |
| US763,179 | 1991-09-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2078616A1 true CA2078616A1 (en) | 1993-03-21 |
Family
ID=25067092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2078616 Abandoned CA2078616A1 (en) | 1991-09-20 | 1992-09-18 | Cathodic protection anode and method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2078616A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6562229B1 (en) | 1997-05-12 | 2003-05-13 | John W. Burgher | Louvered anode for cathodic protection systems |
| ITMI20101689A1 (en) * | 2010-09-17 | 2012-03-18 | Industrie De Nora Spa | ANODE FOR CATHODIC PROTECTION AND METHOD FOR ITS ACHIEVEMENT |
-
1992
- 1992-09-18 CA CA 2078616 patent/CA2078616A1/en not_active Abandoned
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6562229B1 (en) | 1997-05-12 | 2003-05-13 | John W. Burgher | Louvered anode for cathodic protection systems |
| ITMI20101689A1 (en) * | 2010-09-17 | 2012-03-18 | Industrie De Nora Spa | ANODE FOR CATHODIC PROTECTION AND METHOD FOR ITS ACHIEVEMENT |
| WO2012035107A1 (en) | 2010-09-17 | 2012-03-22 | Industrie De Nora S.P.A. | Anode for cathodic protection and method for manufacturing the same |
| CN103119201A (en) * | 2010-09-17 | 2013-05-22 | 德诺拉工业有限公司 | Anode for cathodic protection and method for manufacturing the same |
| US20130168261A1 (en) * | 2010-09-17 | 2013-07-04 | Industrie De Nora S.P.A. | Anode for cathodic protection and method for manufacturing the same |
| AU2011303882B2 (en) * | 2010-09-17 | 2015-01-22 | Industrie De Nora S.P.A. | Anode for cathodic protection and method for manufacturing the same |
| CN103119201B (en) * | 2010-09-17 | 2015-12-16 | 德诺拉工业有限公司 | For anode and the manufacture method thereof of galvanic protection |
| EA024024B1 (en) * | 2010-09-17 | 2016-08-31 | Индустрие Де Нора С.П.А. | Method for manufacturing anode for cathodic protection |
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