JPH0431031B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Cross-references to related applications U.S. patent application serial number filed May 8, 1987
This is a continuation of 47809.

BACKGROUND OF THE INVENTION Steel-reinforced concrete structures, such as bridge decks and parking garages, generally perform well. However, the dramatic increase in the use of road salts, combined with the increase in coastal construction, has resulted in widespread deterioration problems.

One type of attempt to provide cathodic protection of steel in concrete has been slotted non-overlay. Slotted, uncoated anodes have been developed to provide an approach that does not increase the dead load and height of concrete structures. The slot can be filled with a "conductive grout" mixture of carbon and organic resin that serves as the anode surface. Since this conductive grout has limited electrical conductivity, the current is distributed to the anode by a system of platinized metal wire and carbon strand conductors.

Early slotless overcoat systems used platinum-plated wire embedded in Portland cement mortar with a cap of polymer-modified mortar. The backfill failed due to attack by gas and acid generated at the wire surface by anodic reaction.

As discussed in US Pat. No. 4,255,241, a system is shown in which slots are cut into the concrete surface, with care taken to avoid exposing any of the steel reinforcing bars. The bottom of the slot can be covered with plastic tape. A wire anode, such as platinized niobium, is then placed in the slot and the wire is surrounded by carbonaceous conductive backfill. Materials useful for backfilling can include graphite. In practice, this system proved to be labor intensive and, furthermore, the installation exhibited premature failure as indicated by surface cracks or other surface discontinuities in the concrete.

Valve metal electrodes, as exemplified by expanded titanium wire mesh, have recently gained wide acceptance for widespread applications in steel reinforced concrete. As detailed in PCT Published Application No. 86/06759, such electrodes can easily cover large surfaces. They are most advantageous when rolled and unwound on a wide surface such as a flat deck. Such widespread coverage has led to the acceptance of this type of cathodic protection system. Upon installation, the system is provided with an overcoat layer covering the entire system. Such systems therefore not only require wide coverage overcoats, but may also require some adjustment to work around obstacles.

Slotted uncoated systems have therefore not achieved wide commercial acceptance and have not met their promise as a solution for providing cathodic protection to steel reinforced concrete structures. Expanded wire mesh systems can be supplemented with compatible electrodes that are easily designed around irregular surfaces. However, there is a continuing need to provide suitable systems where no overcoat is desired or required, or where it may be useful in the protection of existing concrete structures. There is.

SUMMARY OF THE INVENTION An anode system has been devised which is particularly useful for cathodic protection of concrete and as a slotted or non-slotted system, which system provides improved current distribution for reinforcing steels. It is something. This system can be used in a wide variety of ways, is extremely simple in that it does not require special manual operations, and
It is economical in that it does not require the on-site preparation of special unfamiliar substances or the need to have them on hand at the work site. This system is easily adapted for use on a variety of surfaces, such as overhead surfaces, and around numerous obstacles on such surfaces, while requiring only a bead of overcoat when necessary. It is. Although this system may be prepared in part at off-site locations, it is also useful for on-site installations, such as directly on concrete surfaces.

Broadly considered, the present invention is directed to cathodic corrosion protection for steel reinforced concrete, the system comprising:
the ribbon width is greater than the thickness and the ribbon length is greater than the width, while having an electrochemically active surface coating;
a thin, elongated, corrosion-resistant bulb metal ribbon anode installed on or within a concrete surface but spaced apart from steel reinforcing members in the concrete;
a bead of ionically conductive binder material in sufficient quantity to embed the ribbon anode within the ionically conductive binder material at the concrete surface, the bead having a volume resistivity of less than 50,000 ohm-cm; and a corrosion resistant valve metal current distributor member electrically connected to the ribbon anode and having a greater mass per unit length than the ribbon anode.

In another aspect, the invention is directed to a method of cathodically protecting an existing metal reinforced concrete structure. In other aspects, the invention provides a composite of steel reinforced concrete cathodically protected with a system as described above, and
It is intended for such concrete surfaces with slotted or non-slotted systems applied at the surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, the present invention is suitable for use in any application where reinforced concrete structures require cathodic protection and present horizontal, vertical, sloped, or overhead surfaces for application of the system. Find usability. The invention finds utility in applications where slots can be cut directly on a surface or into the surface of a structure. The present invention finds particular utility on vertical or overhead surfaces where complete coverage of an existing structure with a bonding overcoat is undesirable or impossible.
Accordingly, the corrosion protection system of the present invention is expected to find use in steel reinforced concrete structures such as bridge decks, parking garage floors, bridge substructures, and building structural members.

Referring to FIG. 1, a reinforced concrete structure, indicated generally at 31, is partially shown receiving cathodic protection on its underside. For corrosion protection, a non-porous anode ribbon 32 is provided from a source not shown, such as a coil of ribbon.
the underside 3 of the concrete structure 31 such that one side of it is applied to the face of the concrete structure 31;
Applies to 3. Lower side 33 of anode ribbon 32
During application, the ribbon 32 may first be fastened into the steel reinforced concrete structure 31 with plastic or other non-conductive fasteners, and those fasteners may be inserted into the hollow holes or It may also be adhered to the surface of the structure. After applying the ribbon 32 to the underside 31 of the structure 31, a bead 35 of ionically conductive binding material is applied by a sprayer 34. This bead 35 is on the lower side 3
Anode ribbon 32 remains exposed at 3
cover the face of This application of binding material allows the sprayer 34 to deliver enough beads to embed the anode ribbon 32, but need not cover the entire surface of the underside 33. Several anode ribbons 32 are applied and thus buried,
And, as will be described more specifically below,
After being arranged parallel to each other and usually spaced apart, such anode ribbons 32 are then connected to a current supply (not shown), which in turn is connected to an applied current source.

Referring to FIG. 2, a portion of a concrete structure, such as the edge of a parking garage floor, is shown at 41. This structure 41 has a floor 42 and side walls 43.
has. The edge between the floor 42 and the side wall 43 is interrupted by an obstruction, in this case a standpipe 44, as shown, which runs along the side wall 43 and opens the opening in the floor 42. It stands out throughout. floor 4
To undergo cathodic protection for 2, an anode ribbon 45, not shown, is first applied, for example from a coil. This anode ribbon 45
is easily applied on the floor 42 around the standpipe 44 by first simply bending it back on itself by 180 degrees. Next, in its application plane, ie in the plane of the bed 42, the bent ribbon 45 can be twisted at right angles at a 90 degree angle to its long axis. Following this application of the anode ribbon 45, it can then be embedded in an ionically conductive bonding material, not shown, in a manner similar to that shown in FIG.

Referring now to FIG. 3, a reinforced concrete support structure is depicted, generally indicated at 51, viewed from below. This structure 51 has a vertical surface 52 with rounded edges, as well as a flat lower surface 53 below.
It has The anode ribbon 54 is applied by wrapping around the vertical surface 52 and initially during application can be fastened to the underlying vertical concrete surface 52 in such a manner as with plastic fasteners. On the lower reinforced concrete surface 53, the ribbon is first applied as a flat section 55 on the lower surface 53. Upon reaching the rounded end of the concrete structure 51, the flat portion 55 of the ribbon is bent approximately 90 degrees on its long axis such that the corner end of the anode ribbon 55 becomes an edge portion 56. In this way, the anode ribbon 5
5 is initially in surface contact with the concrete structure 51, but upon bending the ribbon 55 through 90 degrees along the long axis about the corner, it comes into edge contact with the concrete structure. As the path of the ribbon 55 continues around the corner, the ribbon 55 twists back 90 degrees along its long axis and the anode ribbon 55
is again in surface contact with the concrete structure 51. However, it is natural that the anode ribbon could be attached to the corners by many flat folds rather than being curled over the edges. All applied anode ribbons can then be embedded in an ionically conductive bonding material in a manner not shown but as taught in FIG. 1.

Referring now to FIG. 4, the anode ribbon system of the present invention, indicated generally at 10, is partially illustrated. This anode ribbon system 10 has individual anode strips or ribbons 2 which are to be set into slots in the concrete (not shown). These anode ribbons 2 are spaced apart from each other in an at least substantially parallel manner. The anode ribbon 2 has a ribbon end portion 3. As shown in the figure, these ribbon ends are easy to bend since the ribbon configuration allows for the ease of bending the ribbon back by 90 degrees so that the end 3 can be a continuous part of the anode ribbon 2. can be formed. The overall effect is a continuous strip anode, with the anode ribbon 2 continuing as the ribbon end 3, and so on. These ribbon ends 3 are joined to a current supply 4. For good electrical contact between the ribbon ends 3 and the current supply 4, they can be joined by spot welds 5. The current supply 4 is then connected to an applied current source by means not shown.

Referring now to Figure 5, a general overview of the slotted steel reinforced concrete structure is
0. On the surface 12 of this concrete structure 20, the slot 11 is connected to the surface 1.
2 It is cut into the middle. In addition to the anode ribbon slot 11, the concrete surface 12 has a current supply slot 13 cut therein. This surface 12 thus created is then ready for insertion of the anode ribbon and current supply.

For installation, the selection of a concrete surface, such as a parking garage floor, can be followed by a choice between direct application (non-slotted) and slotted applications. If a slotted system is selected, ribbon slots 11 can be cut into surface 12, for example by a saw. The thin ribbon structure allows the saw to cut with a single blade width, or perhaps with two blade widths, rather than requiring multiple grooves to provide the proper opening. It is a particular advantage of the system of the present invention that only a small amount of 100% of the total amount of 0.00000 0.00000 Typically, these saw cuts are parallel lines as shown in FIG. 2, but this need not be the case. Other configurations such as zigzag or arcuate shapes are also expected to avoid obstacles such as pillars. For best protection, those notches should be
They are placed to provide at least more or less equidistant spacing between them, thereby providing uniformity of current emission over the surface protected thereby. When considering the spacing, the distance between the application ribbon anodes 54 or between the slots 11 is economically at least about 15 cm, while this type of spacing usually ensures an even current distribution to the reinforcing steel. To guarantee that the height will not exceed approximately 60cm. Most typically, the spacing between adjacent ribbons in surface applications as incisions will be in the range of about 25 cm to about 40 cm.

Taking these spacings into account, it is possible for the anode ribbon 2 to have a width of about 2.5 cm or less.
Normal is sufficient to effect the desired current discharge into the surrounding concrete. For convenience, only the anode ribbon 2 will be referred to hereafter, but such references will refer to the anode ribbons 2, 32, 4.
It goes without saying that the meaning includes any and all of 5 and 54. Anode ribbon 2 widths greater than about 2.5 cm may be uneconomical. on the other hand,
Anode ribbons 2 having widths less than about 0.25 cm require an uneconomical number of closely spaced ribbons or slots 11. Besides, such anode ribbon 2
is typically about 0.15 cm or less thick and provides the most efficient current flow at low resistance.
And, more typically, it has a thickness of less than about 0.1 cm. On the other hand, for proper current distribution along the anode ribbon 2, the anode ribbon should be at least about
It has a thickness of 0.02cm. In order to provide an advantageous efficient configuration for obtaining a high surface area of the anode ribbon, combined with a homogeneous current distribution into the surrounding concrete, the anode ribbon 2 is most usually of the order of about 0.5 to 0.8 cm wide and about It has a thickness of 0.05 to 0.08 cm.

Thus, the ribbon anode is at least substantially ribbon sized. That is, the ribbon anode has a ribbon width that is at least substantially greater than its thickness. Moreover, it has a ribbon length that is at least substantially greater than its width, as shown for example in the figures. When supplied at the installation site, ribbon anodes are often in coil form for storage and handling efficiency. Typically, such coils include an anode ribbon of 100 meters to 200 meters or longer, although relatively short lengths of coil anode ribbon, for example 10 to 50 meters, can also be used. In terms of thickness and width, ribbon anodes have a width to thickness ratio of approximately
One can expect it to be in the range of 20:1 to about 5:1. Moreover, it has at least a substantially rectangular cross-section, ie generally rectangular in cross-section, but with variants of cross-section, for example a beveled edge where the anode is in the middle of the cross-section and its thickness is large. It is natural to have expectations. This ribbon configuration provides an advantageous aspect ratio, ie, a high ratio of anode surface area to anode length.

The dimensions for the ribbon anode as discussed above provide an anode that can be easily bent back on itself, for example, initially at a 90 degree angle as depicted in FIG.
at an angle of 180 degrees and rotated in its application plane as delineated by corner 46 of
Can be bent back. This provides desirable ease of anode application during installation in rectangular patterns as depicted in Figures 4 and 5, or around corners or obstructions that often occur on concrete surfaces as depicted in Figure 2. It is something. Moreover, the ribbon anode has the desirable ease of being able to bend along its long axis, such as to the extent depicted in the lower surface 53 of FIG. is twisted to an angle such that it meets the underlying concrete surface on its edge. Once past a corner or obstacle, the ribbon anode can again make more normal flat surface contact with the concrete surface. However, especially when the ribbon anode has active coatings on both flat sides,
It should be understood that the entire installation includes a ribbon anode standing at its edges on a concrete surface. When applied over the edge or at an angle, the resulting height of the widest anode is at most about 2.5 cm, which can be easily covered by the binding material. Typically, a layer of such material with a thickness of about 3 cm to about 5 cm is applied over the installed ribbon anode, the surface of which serves as an anti-wear layer, e.g. a anti-traffic layer. It is something that should be done. However, unless it is necessary to embed a ribbon anode standing on the edge, a layer of bonding material at least about 1.2 cm and up to about 3 cm thick may be used, for example, when the ribbon anode is used overhead or in a vertical plane. It is usually applied when

Such an anode ribbon 2, corresponding to these dimensions, would have a density of 200 m2 per square meter of anode area without damaging the surrounding concrete.
Operable current densities of milliamperes (mA/m ² ) can be easily handled. The current density of operation may be on the order of at least about 50 mA/m ² , and the anode as described herein efficiently carries such a load while maintaining homogeneity of current distribution. However, it should be understood that current densities on the order of about 400 to 600 mA/ ^m2 , or even higher, are expected, although densities on the order of 100-300 mA/ ^m2 provide the best steel reinforcement corrosion protection. most advantageous for

Taking into account the above considerations regarding the dimensions of the anode ribbon 2 with respect to the slot system, the slot 11 of the anode ribbon is therefore a cut of sufficient width and depth to facilitate the installation of the ribbon 2.
In this regard, slot depths on the order of about 1.25 to about 2.5 cm are typical. More commonly, such slots 11 are cut to a depth of 1 cm or less, for example on the order of 0.6-0.8 cm. It is desirable to insert the ribbon to a depth such that the ribbon is below the surface of the concrete, and more specifically to a depth of at least 0.1 cm below the surface of the concrete. In order to ensure complete embedding of the anode ribbon 2 during backfilling and thus prevent surface exposure of the anode ribbon 2, the anode slot 11 has an anode ribbon width of about 0.5 to 1.0 cm.
The cut is typically made to a depth of no more than 2.5 to 4 cm, eg, no more than about 2.5 to 4 cm. A slot width of approximately 0.3 cm can be created by making one cut with the saw blade. This can be useful for insertion of the anode ribbon 2, but for easiest backfilling, such as with pumpable grout, the two blades are almost always used together to create a slot of approximately 0.6 cm. is notched, but group use may be utilized to provide a slot width of approximately 1.25 cm.

As shown in FIG. 5, for the slot system the current supply 4 can also be inserted into the slot 13. These slots can be cut into the concrete surface in a similar manner. For slotted or non-slotted systems, such feeder 4
are generally essentially equidistant from each other, although it is not necessary that the current suppliers 4 be as equidistant from each other as is the case for the anode ribbon 2. Also, whether the anode ribbon 2 is on a concrete surface or in a slot, adjacent ribbons typically run parallel to each other, although other configurations are also contemplated. For relatively low current densities, the distance between the current suppliers 4 may be as large as about 100 meters, while for higher current densities, the distance may be as large as 25 to 30 meters.
should be reduced to about 100 m. Normally,
The current supplies are spaced about 50 to about 80 meters apart.

As for the current supplies, it is advantageous that these too are elongated, at least substantially of ribbon size, as mentioned above for ribbon size. Such a shape provides ease of attachment of the anode ribbon to the current supply, either in an edge or vertical position as shown in FIG. 5, or both when horizontal to flat on concrete. However, other forms for the current supply 11 are also contemplated, including a rod. The current supplier as an elongated strip is thicker or wider than the anode ribbon, or thicker and wider, for example about 0.3 in order to distribute the current evenly into such ribbon 2 with minimal IR voltage losses. It is about cm thick and up to about 5 cm wide. Current supply is individual anode ribbon, width 2
It is not uncommon for the width or thickness relationship between the feeder and the anode to be on the order of 1.1:1 to 3:1. It's within the range.
It is therefore envisaged that the slot 13 for the current supplier could have a similar width to the anode ribbon, and even a similar depth, but could be deeper, for example 5 cm. Good too.

When a concrete surface is prepared to receive an anode ribbon cathodic protection system, e.g.
When the slot is configured to receive an anode ribbon therein, the attachment may be accomplished in one manner by unwinding the anode ribbon, typically by unwinding a continuous strip of ribbon from an anode ribbon coil. You can begin by placing it on concrete. In unwinding the coil, the anode ribbon can be placed either along the concrete surface as depicted in FIG. 1, or into cut slots 11 as shown in FIGS. 4 and 5, all in continuous fashion. The current supply 4 may also be placed on the concrete surface. When the anode ribbon 2 is bent to pass between the individual ribbon slots 11 and through the current supply slot 13, the ribbon end 3 can be fastened to the current supply 4. The same system may be used for flat or horizontal applications on concrete surfaces. Any suitable means of providing an adhesive, electrically conductive connection between the anode ribbon and the current supply may be used, such as crimping.
In the field during installation, welding is the most advantageous in terms of efficiency and economy, such as roller welding and spot welding, with spot welding being preferred for best efficiency. After the anode ribbon has been distributed, such as by coil unwinding and fastening to the current supply, the system can be coated or the anode ribbon 2 and current supply 4
It may be first installed by simply sliding it into the slot 11. Alternative methods may be used, for example, cutting the anode ribbon to essentially a predetermined length but with a terminal lug and then fastening the lug to the current supply.

After inserting the anode ribbon 2 and current supply 4, the slots 11 and 13 can then be backfilled. Unless the slots 11 and 13 are cut to such a depth as to endanger the contact between the anode ribbon 2 or the current supply 4 and the steel reinforcing elements of the concrete structure, the anode ribbon 2 and the current supply No preparation of slots 11 and 13 before installation with 4 is necessary. Figure 1
For surface applications such as those shown in Figure 1, the anode ribbon 32 need only be placed on the surface and typically fastened thereto. For backfilling, i.e. burial of surface-applied anode ribbons, approximately 50,000 ohm cm
Any ionically conductive binder material with lower volume resistance is suitable. In this way, special in-situ formulation and compounding of rarely used backfill coatings or surface coatings is not required. moreover,
The backfill must not be a conductive carbonaceous backfill or other such conductive backfill;
This is because it results in carbonaceous material becoming anodically active, which may cause damage to the surrounding concrete. Typical bonding backfills or surface coverings that can be used include non-shrinking, self-leveling, pumpable grouts, Portland cement, and other cements, most typically about 20,000 ohms. It has a volumetric resistance lower than cm.

Backfill is almost always applied in an amount sufficient to fill the anode-containing slot 11, the current supply-containing slot 13, and the slots 11 and 13 at least flush with the reinforced concrete surface. In surface applications, the applied material is sufficient to completely fill the anode 32.
Such application results in complete coverage of the anode ribbon and current supply. If parts of the current supply extend beyond the surface, for example below the bridge deck, such parts of the current supply need not be so embedded in the backfill. It is also expected that this anodic ribbon system may be useful when overcoating is included in the finishing operation, especially for abrasion resistant surfaces. Such a topcoat may be any that is useful in the operation of providing a topcoat to reinforced concrete structures.

As previously mentioned, the anode ribbon can be placed in a non-slotted application on a reinforced concrete structure, such as a bridge or building support column, as well as in a flat surface mount. Such applications may be particularly useful for applications in the vertical plane. The anode ribbon in such surface mounts can be in parallel strips, or it can be spirally wrapped around the column, or it can be arcuate or zigzag or other shape. Dimensional and spacing aspects for both the anode ribbon and current supply are as discussed above. The anode ribbon is uncoiled onto the concrete surface, fastened by any suitable means for fastening metal anodes to concrete, and then overcoated, all as discussed above. be.

Following installation of the anode ribbon system, a current supply is electrically connected to the positive terminal of a suitable current source and the reinforcing steel of the concrete structure is connected to the negative terminal of the power source. A direct current suitable for cathodic protection of this reinforcing steel is then applied. Any power source suitable for use with cathodic protection assemblies to act in protecting concrete, such as in bridge decks, parking garages, etc., is useful in the present invention. The ribbons for both the anode ribbon and the current supplier are metal ribbons. Advantageous for good electrical conductivity and durability, such metals for the ribbon and current supply are titanium, tantalum, zirconium, or niobium. In addition to the elemental metals themselves, suitable metals for the ribbon and current supply may include alloys of these metals with themselves and with other metals, as well as intermetallic mixtures thereof. Of particular interest is titanium because of its toughness, resistance to corrosion, such as in concrete environments containing chloride impurities, and availability. Typical of such metals that can be used are grade 1 titanium, annealed titanium with low brittleness. Such features are advantageous in allowing ribbon installation without deleterious ribbon breakage. Moreover, alloying may increase the brittleness of elemental metals and therefore suitable alloys may have to be chosen carefully.

The metal ribbon can be made directly from the selected metal by such methods as by cutting a sheet or coil of valve metal lengthwise to the desired width of the ribbon, with the sheet or coil itself providing the desired ribbon thickness. . After lengthwise tearing, the resulting ribbon can be easily wound into a coil form, for example, for storage or transportation for later operations.

The anode ribbon can be applied as a final step in its preparation. The coating may be applied to both flat sides of the ribbon anode as well as to the edges of the anode, for example, by first dipping the ribbon anode into the coating composition. This method can be particularly useful when the anode is used standing on an edge, either in a slot or on a concrete surface. When the ribbon anode is mounted on a surface, but flat to that surface, it is anticipated that for some installations only the flat side of the ribbon anode facing the concrete surface will need to have an active coating. . The ribbon may also be coated before it is ribbon-shaped, thereby allowing shaping, e.g. cutting,
It is understood that the width of the ribbon has coverage while the thickness of the ribbon has no coverage. Whether applied before or after ribbon formation, the substrate is particularly useful for supporting catalytically active materials, thereby allowing the formation of catalytic structures. As an aspect of its use, the ribbon support can have a catalyst coating to provide an anode structure. Usually beforehand, the valve metal ribbon is subjected to a cleaning operation, for example a degreasing operation,
The operation can include etching in addition to cleaning, as is well known in the art of preparing valve metal to receive electrochemically active coatings. It is also well known that a valve metal, which may also be referred to herein as a "film-formable" metal, will not function as an anode without an electrochemically active coating that prevents its passivation. The electrochemically active coating may be provided by platinum or other platinum group metals, or by a number of active oxides such as platinum group metal oxides, magnetites, ferrites, cobalt spinels, or mixed metal oxide coatings. It can be any of the chemical coatings that have been developed for use as anode coatings in the electrochemical industry. It is particularly preferred for long-term protection of concrete structures that the anode coating is a mixed metal oxide, which can be a solid solution of a film-forming metal oxide and a platinum group metal oxide.

For this long-term corrosion protection application, the coating should be present in an amount of 0.025 to about 0.5 grams of active coating per square meter of valve metal ribbon. An active coating of, for example, a platinum group metal of about 0.025 grams or less may serve to prevent passivation of the valve metal substrate over long periods of time or may function economically at sufficiently low unipolar potentials to improve the selectivity of the anodic reaction. gives an insufficient electrochemically active coating to improve the On the other hand, the presence of more than about 0.5 grams of active coating, or more often more than about 0.25 grams of platinum group metal, per square meter of valve metal ribbon is costly without resulting in a commensurate improvement in anode life. Scatter. In this particular embodiment of the invention, the mixed metal oxide coating is highly catalytic for oxygen evolution reactions and does not generate chlorine or hypochlorous acid at low current densities in concrete environments containing chloride impurities. . Platinum group metal oxides or mixed metal oxides for coatings are disclosed in US Pat. No. 3265526; 3632398;
3711385 and 4528084. More specifically, such platinum group metals include platinum, palladium, rhodium, iridium, and ruthenium, or alloys of themselves with other metals. Mixed metal oxides include at least one of these platinum group metal oxides in combination with at least one oxide of a valve metal or another non-noble metal. Economically, the coating is U.S. Patent No.
4528084 is preferred.

In the installed anode ribbon system, the anode ribbon 2 is connected to a current supply 4, for example the metal strip current supply 4 of FIG. Such feeder 4 is almost always a valve metal, preferably an alloy or intermetallic mixture containing the same metal as that most predominately found in the valve metal anode ribbon 2. This current supply 4 must be firmly attached to the metal anode ribbon 2. Such a method of firmly fixing the feeder 4 to the ribbon 2 can be by welding, as described above. Additionally, welding can proceed through the coating. Therefore, the coated ribbon current supply 4
can be pressed toward the coated anode ribbon 2 with their respective coated surfaces in contact, and welding can still proceed easily. The ribbon current supply 4 can be sufficiently welded to the anode ribbon 2 to provide a homogeneous current distribution.

In installed anode ribbon systems, the buried parts of the current supply 4 may also be coated, for example with the same electrochemically active coating of the anode ribbon 2, but almost always the current supply 4 is coated with remains unresolved. If coated,
The same considerations regarding coating weight, for example for the anode ribbon 2, are also important for the current supply 4. These feeders 4 may be fixed to the anode ribbon 2 before or after coating. The current supply 4 can then be connected to a current conductor outside the concrete environment, and the current conductor outside the concrete need not be so coated. In a concrete bridge deck, for example, the current supply may include a rod extending through a hole to the underside of the floor and upwardly to where the strip current supply 4 is located. In this way, the mechanical current connections can be made outside the finished concrete structure and are therefore easily available for access and use if required. Connections to the current distribution rods outside the concrete may be by conventional mechanical means such as bolted spade-lug couplings.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a portion of the underside of a concrete structure undergoing cathodic protection using a ribbon anode. FIG. 2 is a perspective view of a portion of a concrete structure undergoing cathodic protection around an obstruction. FIG. 3 is a perspective view of a reinforced concrete bridge support structure with ribbon anodes installed. FIG. 4 is a perspective view of a portion of a ribbon anode assembly erected on an edge for installation in slotted reinforced concrete. FIG. 5 is an overhead view of a slotted reinforced concrete structure, such as a bridge deck, being constructed for the assembly of FIG.

Claims (1)

Claims: 1. An applied current protection system for steel-reinforced concrete, comprising: each at least substantially rectangular in cross-section, with a width ranging from 0.25 cm to 2.5 cm;
while its thickness is in the range 0.02 cm to 0.15 cm and the width to thickness ratio is at least 5:1, so that it has a ribbon width greater than its thickness and a ribbon length greater than its width; an anode of a thin, elongated, corrosion-resistant valve metal ribbon with a chemically active surface coating on or in the concrete surface but spaced from the steel reinforcing elements in the concrete; a bead or layer of ionically conductive, non-carbonaceous binding material, the bead or layer being sufficient to embed the ribbon anode within the binding material at the surface of the concrete; , the above-mentioned binding substance has a volume resistance smaller than 50000 ohm cm,
an applied current for steel reinforced concrete comprising: a bead or layer; a current distributor member of corrosion resistant valve metal electrically connected to said ribbon anode and having a mass per unit length greater than said ribbon anode; Protective system. 2. The applied current protection system of claim 1, wherein the ribbon anode is installed above a concrete surface, horizontally, slanted, vertically or overhead. 3. An installed ribbon anode has one side of the ribbon applied on the concrete, and the anode is configured such that the applied bead of bonding material is sufficient to embed the ribbon anode but covers all of the concrete surface. 3. The applied current protection system of claim 2, wherein the applied current protection system is spaced sufficiently apart to provide sufficient shielding. 4. The installed ribbon anode has one side of the ribbon applied on the concrete surface, and the applied bead of binding material is sufficient to embed the ribbon anode and simultaneously cover all of the concrete surface. 3. The applied current protection system of claim 2, wherein the applied current protection system is in a sufficient amount. 5. The applied current protection system of claim 1, wherein said ribbon anode is installed in a cut slot in the surface of said concrete, said slot being no greater than 4 cm deep and 1.25 cm wide. 6. Applied current protection system according to claim 5, wherein said system comprises a number of adjacent slots containing said valve metal ribbon, said adjacent slots being spaced from each other at a distance in the range from 15 to 60 cm. . 7. The applied current protection system of claim 5, wherein said slot is backfilled with said ionically conductive binding material. 8. The applied current protection system of claim 5, wherein said backfill slot containing said ribbon anode is covered with a concrete overcoat. 9. The applied current protection system of claim 1, wherein the binding material is a non-shrinking, self-leveling, pumpable grout with a volume resistivity of less than 20,000 ohm-cm. 10. The application of claim 1, wherein the valve metal ribbon anode and the valve metal current distributor member each comprise a metal selected from the group consisting of titanium, tantalum, zirconium, niobium, alloys thereof, and intermetallic mixtures. Current protection system. 11. The applied current protection system of claim 1, wherein said ribbon anode is electrically resistance welded to said current distributor member, said anode being in face-to-face contact with said member. 12. The applied current protection system of claim 11, wherein the current distributor member electrically connected to the ribbon anode does not include an electrochemically active surface coating. 13 The current distributor member is an elongated current distributor member, with a width of not more than 5 cm and a thickness of 0.3 cm.
2. The applied current protection system of claim 1, having an at least substantially rectangular cross-section, not greater than cm, with a width in the range of 3:1 to 1.1:1 relative to the width of the ribbon anode. 14 The current distributor member is inserted at least partially into the cut slot in the surface of the concrete, with adjacent slots being 25 to 100 mm apart from each other.
spaced at a distance within m,
The applied current protection system according to claim 1. 15. The applied current protection system of claim 1, wherein the current distributor member is connected to a power source that applies an operating current of 50 to 600 mA/ ^m2 on the ribbon anode. 16 The applied current cathodic protection system comprises a series of thin, elongated, corrosion-resistant valve metal ribbon anodes having an electrochemically active surface coating, the active anode being spaced from a steel reinforcing member in the concrete. and the ribbon anodes are spaced apart from each other, and the anodes are electrically connected to the current distributor member, while the ionically conductive and non-conductive ribbons applied to the anodes are In applied current cathode protection systems for steel-reinforced concrete embedded in a carbonaceous bonding material, a thin, elongated, corrosion-resistant valve metal current distributor with a greater mass per unit length than the ribbon anode described above. consisting of members, each member having at least a substantially rectangular cross-section, each having a width of 5 cm or less, a thickness of 0.3 cm or less, and a ratio of the width to the width of the ribbon anode from 3:1 to 1.1. :1, wherein the current distributor member does not include the active surface coating even on the portion of the member that is electrically connected to the ribbon anode, and the portion is thereby coated with the binding material. Applied current cathode protection system for steel-reinforced concrete that can be buried inside. 17. A method of inhibiting corrosion in a steel reinforced concrete structure, comprising the steps of:
Widths ranging from 0.25cm to 2.5cm and 0.02cm to 0.15cm
and a width to thickness ratio of at least 5:1 such that the ribbon width is greater than the thickness and the ribbon length is greater than the width, and each ribbon anode is electrochemically active. applying a thin, elongated, corrosion-resistant valve metal ribbon anode with a surface coating that is placed on or within the concrete surface but spaced from the steel reinforcement in the concrete; electrically conductive, non-carbonaceous; applying a bead or layer of adhesive bonding material in sufficient quantity to embed the ribbon anode within the bonding material on the concrete surface;
the binding material has a volumetric resistance of less than 50000 ohm cm; the applied current steering anode is electrically connected to a corrosion-resistant valve metal current distributor member having a greater mass per unit length than the ribbon anode; A method for inhibiting corrosion in steel-reinforced concrete structures, comprising: 18. The method of claim 17, wherein the ribbon anode is applied to a horizontal, inclined, vertical or overhead concrete surface. 19 said ribbon anode is applied flat and well spaced on said concrete surface;
Thereby, said applied bead of binding material is
18. The method of claim 17, wherein the method is sufficient to embed the ribbon anode, but not enough to cover all of the concrete surface. 20. Claim 17, wherein said ribbon anode is applied to a cut slot in said concrete surface.
Method described. 21 The ribbon anode is first placed in the slot, the current distributor member is placed, and the portion of the ribbon anode adjacent to the current distributor member is removed from the slot and electrically connected to the current distributor member. 21. The method of claim 20, further comprising connecting and returning the resulting connecting ribbon anode to the slot. 22. The method of claim 17, wherein the applied ribbon anode is electrically resistance welded to the current distributor member. 23. The method of claim 17, wherein the binding material applied to the ribbon anode is a pumpable grout with a volume resistivity of less than 20,000 ohm-cm. 24. The method of claim 17, wherein the current distributor member is connected to a power source that applies an operating current of 50 to 600 mA/ ^m2 on the ribbon anode. 25. An applied current cathode protection system for steel-reinforced concrete, wherein the metal anode is placed on the concrete surface, spaced apart from the steel-reinforced member for the concrete, and is particularly adapted for application to overhead and vertical surfaces. the systems are each at least substantially rectangular in cross-section, have a width in the range from 0.25 cm to 2.5 cm, and a thickness in the range from 0.2 cm to 0.15 cm;
the width to thickness ratio is at least 5:1;
The result is a thin, elongated, corrosion-resistant bulb metal ribbon anode with a ribbon width greater than its thickness and a ribbon length greater than its width, each ribbon anode being sufficiently thin to extend at least substantially 180° above itself. the anode ribbon is easily bent and then twisted at the bend in a direction perpendicular to the longitudinal axis of the ribbon to provide a sharp anode corner in the mounting plane on the concrete; The anode can be easily twisted along its long axis by an angle of 90° during application to the concrete, so that the anode is formed into an initially flat anode between the concrete and the anode surface during installation. Proceeding along its long axis from surface contact, then twisting 90° into contact with the concrete and anode edge, and then
Twisted 90 degrees back to flat anode surface contact, each of the ribbon anodes having an electrochemically active surface coating and having a greater mass per unit length than the ribbon anodes, elongated corrosion-resistant bulb metal current distributors. electrically connected to the vessel components; applied current cathodic protection system for steel reinforced concrete. 26 The ribbon anode has at least a substantially rectangular cross section, a width in the range of 0.25 to 2.5 cm, 0.02
and a width-to-thickness ratio ranging from 20:1 to 5:1, thereby having a ribbon width substantially greater than the thickness, while also having a width 26. The applied current cathode protection system of claim 25, having a ribbon length that is substantially greater. 27. The application of claim 25, wherein said valve metal ribbon anode and said valve metal current distributor member each comprise a metal selected from the group consisting of titanium, tantalum, zirconium, niobium, alloys thereof, and intermetallic mixtures. Current cathode protection system. 28. Claim 25, wherein said valve metal anode has an electrochemically active surface coating comprising a platinum group metal or metal oxide, said coating comprising from 0.025 to 0.5 grams of catalytic metal per square meter of said ribbon anode. Applied current cathode protection system. 29. The applied current cathode protection system of claim 25, wherein said electrochemically active surface coating comprises at least one oxide selected from the group consisting of platinum group metal oxides, magnetites, ferrites, and cobalt oxide spinels. 30. The applied current cathode protection system of claim 25, wherein said electrochemically active surface coating comprises a mixed crystalline material of at least one oxide of a valve metal and at least one oxide of a platinum group metal. 31. Said ribbon anode is electrically resistance welded to said elongated current distributor member, said anode and said member being in face-to-face contact.
Applied current cathode protection system as described. 32. said elongate current distributor member has a width not greater than 5 cm and a thickness not greater than 0.3 cm;
The width to the width of the ribbon anode is from 3:1.
26. The applied current cathode protection system of claim 25, having an at least substantially rectangular cross-section within the range of 1.1:1. 33. The applied current cathode protection system of claim 25, wherein the current distributor member is connected to a power source that applies an operating current of 50 to 600 mA/ ^m2 on the ribbon anode.