JPH0551678B2 - - Google Patents

Description

Claim 1: A valve metal in which the shaped units have substantially diamond-shaped voids with LWDs and SWDs, the shape of the voids being interconnected at nodes and carrying an electrochemically active coating on the surface. In a steel-reinforced reinforced concrete cathodic protection electrode consisting of a valve metal mesh defined by a continuum of strands, the valve metal mesh is a flexible mesh with a strand thickness of less than 0.125 cm and a porosity of 90% or more. , the flexible mesh is capable of being coiled and uncoiled around an axis along the LWD length of the diamond-shaped unit;
It can be stretched by up to 10% along the SWD length and can be bent in the general plane of the mesh with a bending radius ranging from 5 to 25 times the mesh width, thereby converting the electrode from a coiled configuration onto the support surface. An electrode for cathodic protection of steel-reinforced reinforced concrete, characterized in that it is possible to unwind the mesh and stretch the mesh on the support surface into the shape of an operating electrode.

2. The electrode of claim 1, wherein said valve metal has an elongation in the range of 20 percent to 40 percent.

3. The electrode of claim 1, wherein the valve metal of the mesh is selected from the group consisting of titanium, tantalum, zirconium, niobium, alloys and intermetallic mixtures thereof.

4. The electrode of claim 4, wherein said valve metal is an annealed, unalloyed metal selected from the group consisting of titanium, tantalum, zirconium and niobium.

5. The electrode according to claim 1, wherein the mesh weight of the valve metal is within the range of 0.05 to 0.5 kilograms of metal per square meter of the mesh.

6. The electrode of claim 1, wherein the mesh is expanded from a coil or sheet of solid bulb metal by a factor ranging from 10:1 to 30:1.

7 The mesh strands have a thickness ranging from 0.05 cm to 0.125 cm and
An electrode according to claim 1 having a width in the range 0.05 cm to 0.20 cm.

8. Said node has a thickness twice the strand thickness and, when in an uncoiled configuration, lies in a vertical plane that is at least substantially completely angular to the horizontal plane of said mesh. 2. An electrode according to claim 1, wherein the electrode is arranged as claimed in claim 1.

9. The electrode according to claim 1, wherein the mesh has a bending radius in the general metal plane in the range of 10 to 20 times the width of the mesh.

10. The electrode according to claim 1, wherein the mesh is comprised of a continuous network of strands connected by a number of nodes, providing a margin for the current carrying path through the mesh.

11. The electrode of claim 1, wherein the strands provide a continuous network of strands giving the shape of voids and interconnected by 500 to 2000 nodes per square meter of mesh.

12 wherein said interconnected metal strands are
2. An electrode according to claim 1, forming a substantially diamond-shaped hole with a long design in the range of 4 to 9 cm and a short design in the range of 2 to 4 cm.

13. The electrode of claim 1, wherein the valve metal mesh is in a coiled form that can be easily unwound.

14. The electrode of claim 13, wherein said coil has an inner hollow region of diameter greater than 20 centimeters and an outer diameter of substantially less than 50 centimeters.

15. The electrode of claim 1, wherein said valve metal mesh is in an uncoiled, at least substantially flat configuration.

16. The electrode according to claim 1, wherein the surface area of the valve metal strand and its connecting portion is 10% or more and 50% or less of the mesh area.

17. The electrode of claim 1, wherein the electrochemically active surface contains a platinum group metal or metal oxide.

18 The above-mentioned coating is applied per square meter of mesh.
18. An electrode according to claim 17, containing from 0.05 to 0.5 grams of catalytic metal.

19. Claim 1, wherein the electrochemically active surface contains at least one oxide selected from the group consisting of platinum group metal oxides, magnetites, ferrites, and cobalt oxide spinels. Electrodes described in Section.

20. The electrode of claim 1, wherein the electrochemically active coating contains a mixed crystal material of one or more valve metal oxides and one or more platinum group metal oxides.

21. The electrode of claim 1, wherein the valve metal is titanium and the electrochemically active coating is a mixed crystal material consisting essentially of titanium oxide and ruthenium oxide.

22. Current is distributed to the valve metal mesh by a valve metal current distribution member metallurgically bonded to the strands of the mesh.
Electrodes described in Section.

23. According to claim 22, the current distribution material is coated with an electrochemically active coating, and the coated member is welded by an electrical resistance method with the coated surface to the coated mesh. Electrode as described.

24. The electrode of claim 1, wherein the operating electrode is in an unwound state on the support surface of the operating electrode shape when the operating electrode carries the operating current.

25. A succession of thin valve metal strands endowed with substantially diamond-shaped voids with shape units LWD length and SWD length, the void shapes interconnected at nodes and carrying an electrochemically active coating on the surface. A method of manufacturing a cathodic protection electrode for steel-reinforced reinforced concrete of the type consisting of a valve metal mesh defined by a body, comprising: (a) extending along the direction of a diamond-shaped SWD length; coiled around an axis along the direction, 90
Thickness 0.125cm with porosity of more than %
(b) coating a surface of the valve metal mesh with an electrocatalyst while the valve metal mesh is coiled, provided that the mesh is not connected to an electrode; A method of manufacturing a cathodic protection electrode of steel-reinforced reinforced concrete, which is capable of being unwound from a coiled configuration for use as a material.

26. The coiled mesh is contacted with a liquid coating composition to apply an electrocatalytic coating having a coating weight of less than 0.5 grams of platinum group metal per square meter of metal mesh substrate. The method described in section.

27. The method of claim 25, wherein said coating is applied by dipping the mesh in a coating composition and rotating the mesh while dipping in said composition.

28 The coil-wound mesh is coil-wound from an expanded metal mesh obtained by expanding a solid metal sheet or coil at an expansion ratio of 10:1 or more to a porosity of 90% or more. The method described in.

29. The method of claim 25, further comprising unwinding the metal mesh electrode from the coiled configuration and welding a valve metal current distribution member to the unwound metal mesh electrode. .

30 A valve metal current distribution member carries an electrocatalytic coating on its surface, and one or more coated surfaces of the distribution member are welded to the valve metal mesh coated surface at the junction of the valve metal mesh current strands. 30. The method of claim 29, wherein:

BACKGROUND OF THE INVENTION The most important development in electrolytic electrodes in recent years has been the advent of dimensionally stable electrodes according to the teachings of US Pat. Nos. 3,771,385 and 3,632,498. This dimensionally stable electrode consists of a valve metal base material, a titanium substrate carrying an electrocatalytic coating, typically a mixed oxide of a platinum group metal, and a mixed crystal or solid solution. The valve is made of metal to form. A large number of different coating compositions have been proposed.

The primary use of dimensionally stable electrodes is as anodes in chlor-alkali production in mercury cells, diaphragm cells, and more recently ion exchange membrane cells. Other applications include oxygen generating anodes for metal electrolytic processes, hypochlorite and chlorate production, metal plating anodes, etc. Applications have also been proposed as cathodic protection anodes and as anodes in some processes.

These dimensionally stable valve metal electrodes are proposed in various shapes depending on the application, such as rods, tubes,
An array of rods or blades mounted on a plate and a conductive support assembly, or a mesh of expanded valve metal, typically diamond-shaped, mounted on a conductive support assembly to provide the necessary stiffness. Complex structures such as those with voids have been proposed.

Although electrodes in the form of platinized bulb metal wires are known for cathodic protection, in all other practical applications electrode stiffness and dimensional stability are important factors for successful operation. For example, many electrolytic cells are operated with electrode spacing of only a few millimeters, making electrode planarity and rigidity extremely important.

This dimensionally stable electrode is operated at relatively high current densities in most applications, typically 3-5 KA/m 2 for ion-exchange membrane cells and 1 KA/m ² for diaphragm cells.
-3 KA/m ² , and 6-10 KA/m ² for mercury electrodes. This high current density, combined with the requirements for planarity/rigidity, requires a valve metal structure with substantial current carrying ability and strength.

A typical known valve metal electrode of the type having an expanded titanium mesh as an operating surface uses a mesh with an expansion ratio of 1.5 to 4 times and a void area of 30 to 70 percent. Although such titanium sheets are somewhat flexible during the manufacturing process, the inherent elasticity of the sheet is typically reduced by a conductive structure with one or more reinforcements extending parallel to the SWD length of the diamond-shaped aperture. There are restrictions due to welding. Such electrode sheets typically have a current carrying capacity of 2-10 A per square meter of electrode surface area.

Other electrode shapes are known for special purposes, such as a rigid cylindrical valve metal sheet mounted on a linear type anode structure for cathodic protection. (See US Pat. No. 4,515,886.) The manufacture of known electrodes typically involves assembling the electrode valve metal structure, for example by welding, followed by degreasing/
It consists of applying a surface treatment such as etching/sandblasting and applying an electrocatalytic coating by various methods including chemical deposition, electroplating and plasma spraying. Chemical deposition consists of applying a coating solution to the electrode structure by dipping or spraying, followed by calcination in an oxidizing atmosphere, usually air.

SUMMARY OF THE INVENTION It has been discovered that titanium and other valve metals such as tantalum and zirconium can be significantly expanded to form substantially diamond-shaped shapes with very high porosity. This expansion results in an acceptable material cost and creates an ideal structure for cathodic protection. Furthermore, this greatly expanded mesh is flexible and
Coil winding and unwinding around an axis along the LWD length is possible. That is, the expanded metal can be supplied in the form of a large roll and easily unrolled over the surface to be protected against corrosion, such as a concrete floor or foundation.
The void geometry of the mesh is defined by a series of valve metal strands interconnected at nodes and carrying an electrocatalyst coating on the surface. These multiple strands provide room for current flow in the event that one or more strands break during shipping or installation. The metal mesh is desirably stretchable along the SWD length of the shape unit, so that a coiled roll of mesh can be unwound and stretched on a support substrate to form the shape of the operating electrode.

The electrode system of the invention satisfies all requirements regarding cathodic protection of reinforced steel in concrete. The electrode system consists of highly expanded valve metal activated with an electrocatalytic coating. Welded valve metal contacts allow electrical current to be distributed to the expanded valve metal. The presence of a large number of current paths in the expanded metal structure provides margin for current distribution and therefore very good current distribution into the reinforced steel. Installation is simple, as over 100 square meters of electrodes can be easily rolled over the surface of a concrete floor or cut to size, and can also be wrapped around a concrete foundation. However, the coated mesh of the present invention
Electrocatalytic coatings on valve metal substrates are useful and can be used in any operation with current density operating conditions of up to 10 amps per square meter of mesh area.
The characteristics of cathodic protection in concrete and the installation of coated meshes for such protection are described in the recently filed application no.
E00182-02C&D), the teachings of which are hereby incorporated by reference.

The electrocatalytic coating used in this invention allows the anode to operate at very low unit electrode potentials, with cathodic protection
It is expected to have a lifespan of more than a year. Unlike other anodes previously used for cathodic protection of steel in concrete, the anode of the present invention is completely dimensionally stable and does not generate carbon dioxide or chlorine from chlorine-contaminated concrete. .
Furthermore, the cathode of the present invention has sufficient surface area so that the acid generated from the anodic reaction does not have a deleterious effect on the surrounding concrete.

In a broad sense, the present invention relates to an electrode for an electrochemical process consisting of a substantially diamond-shaped valve metal mesh having LWD length and SWD length in units of shape, and the shape of the void is such that the valve metal mesh has a thickness. A flexible mesh of porosity greater than 80% made of strands less than 0.125 cm defined by a continuum of valve metal strands interconnected at nodes and carrying an electrochemically active coating on their surfaces. , the flexible mesh described above can be coiled and uncoiled around an axis along the length of the LWD of the shape unit;
It can be stretched by up to 10% along the SWD length and further bent around a bending radius in the general plane of the mesh over a range of 5 to 25 times the mesh width, thereby converting the electrode from a coiled configuration to a support surface. The top can be unrolled and the mesh stretched onto its support surface into the shape of the working electrode.

The present invention also relates to a technique for rapidly and economically coating highly elongated coil wound mesh. Such a technique makes it possible to achieve highly favorable coating results, without causing harmful strand breakage, even on the more delicate meshes of valve metals that are significantly expanded and have extremely high void volumes. Compared to the prior art for manufacturing valve metal electrodes, considerably larger electrode areas, for example about 100 or 200 square meters or even more, can be covered in continuous extension. Furthermore, this economical coating operation can be initiated and completed using readily available equipment in existing facilities with conventional coating equipment.

With regard to this coverage, the present invention provides
It relates to a method of manufacturing an electrode for electrochemical processes of the type consisting of a valve metal mesh endowed with a substantially diamond-shaped void geometry having an LWD length and an SWD length, the void geometry interconnecting at the nodes. (a) providing a flexible coiled valve metal mesh; It is a street and has a void shape.
(b) While the valve metal mesh is being coiled, an electrocatalyst coating is applied to its surface to create a flexible coiled shape. the mesh electrode, provided that the mesh can be unwound from its coiled configuration for use as an electrode.

Other important features of the invention are greatly expanded valve metal meshes and methods of manufacturing such greatly expanded meshes.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a diamond-shaped unit of the greatly expanded valve metal mesh of the present invention.

Figure 2 specifically shows a diamond-shaped structure, with a current distribution section along the LWD length.
FIG. 3 is a partial view of a greatly expanded valve metal mesh welded at nodes;

FIG. 3 is an enlarged view of the mesh node, particularly showing the double strand thickness at the node.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The metal of the valve metal mesh will be exclusively one of titanium, tantalum, zirconium and niobium. Preferred metals for mesh include elemental metals themselves, alloys of these metals with other metals, and intermetallic mixtures thereof.
mixture). Titanium is of particular interest in terms of roughness, corrosion resistance, and availability.
When manufacturing mesh by expanding metal sheets,
Useful sheet material metals will be exclusively annealed metals. A typical example of a useful annealed metal is grade I titanium, annealed low brittle metal, which is necessary because when manufacturing mesh by expanding metal sheets, such sheets must have an elongation of more than 20%. It is. This elongation is a percentage of the elongation measured on a 5 cm (2 inch) sheet having a thickness of 0.0635 cm (0.025 inch) or more at room temperature, for example 20°C.
Expansion metals with an elongation of less than 20 percent are too brittle;
It may be difficult to reliably expand into a useful mesh without deleterious strand breakage.

To eliminate strand breakage in metals used for expansion, metals having an elongation greater than or equal to about 24 percent and substantially always less than or equal to about 40 percent may be advantageous. Metals like aluminum are
It is not contemplated or useful for the mesh of the present invention. Aluminum is particularly unsuitable due to its lack of corrosion resistance. Annealing is also important for useful metals; for example, in the case of tantalum metal, an annealed sheet can be expected to elongate about 37 to 40 percent, but in the unannealed form, the elongation is only about 3 to 5 percent. It cannot be used at all for the preparation of mesh. Moreover, alloying can also add embrittlement to elemental metals, and appropriate alloys must be carefully selected. For example, titanium-palladium alloys, commercially available as grade 7 alloys and containing as much as 0.2 weight percent palladium, have an elongation of about 20 percent or more at room temperature and can be used, although expensive, especially in annealed form. It is. Furthermore, when considering alloys, the expected corrosion resistance of the particular alloy being selected must be taken into account. For example, grade I
Titanium is commonly available containing 0.2 weight percent iron, although Grade I titanium is available containing less than about 0.05 weight percent iron for better corrosion resistance. Generally, this low iron content titanium is suitable for many applications due to its high corrosion resistance.

A metal mesh is then prepared directly from the selected metal. To obtain the best roughness for extending the life of the metal mesh, it is preferable to expand the sheet or coil of valve metal into the mesh. However, it is contemplated that alternative meshes to expanded metal meshes may also be used. Such an alternative consists of corrugating thin metal ribbons and
Individual cells, such as hunk cells, can be made from ribbons by welding them together. A slitter or corrugation device would be useful in preparing the metal ribbon, and automatic resistance welding could be used to prepare the large-void mesh. A suitable expansion technique allows a mesh of interconnected metal strands to be obtained directly. Typically, if a metal of appropriate elongation is selected, very useful meshes without strand breakage will be prepared using such expansion techniques. By using extremely useful annealed valve metals that have the desired roughness and the necessary elongation properties, the expanded mesh can be stretched slightly to form the desired shape during mesh installation. This is particularly useful where non-uniform substrate surfaces or features are most easily protected by applying such extensible meshes. Generally, a roll of Grade I titanium mesh having properties as described in the Examples below will have an extensibility of up to about 10 percent. Furthermore, the mesh thus obtained has a radius of about 5 of the mesh width around the general in-plane bending radius.
It can be expected to be bendable within a range of 25 to 25 times.

When expanding a mesh from a metal sheet, the interconnected metal strands will have a thickness dimension that corresponds to the thickness of the original planar sheet or coil. Typically, this thickness will be within the range of about 0.05 centimeters to about 0.125 centimeters. Using a sheet with a thickness less than about 0.05 centimeters not only results in a detrimental number of broken strands during the expansion operation, but also results in a material that is too flexible to be difficult to handle. Sheets larger than about 0.125 centimeters are avoided for economic reasons. As a result of the expansion operation, the strands are interconnected at the nodes, where the thickness of the nodes is twice the thickness of the strands. That is, the thickness of the node is within the range of about 0.1 centimeter to about 0.25 centimeter. Furthermore, the special mesh node after expansion will be completely or substantially completely square. The foregoing is meant to mean that the plane through the thickness of the node is completely or substantially completely perpendicular to the horizontal plane of the unwound mesh roll.

When considering the preferred valve metal titanium, the mesh weight is typically approximately
In the range of 0.05 kg to about 0.5 kg. This range takes titanium metal as an example, and is not necessarily a useful range for general valve metals. Titanium is the valve metal with the lowest specific gravity. Ranges for various valve metals can be calculated based on their specific gravity relationship with titanium. Again using titanium as an example, a weight of less than about 0.05 kilograms per square meter of mesh may not be sufficient to provide adequate current distribution in enhanced cathodic protection. On the other hand, weights greater than about 0.5 kilograms per square meter will be uneconomical for most mesh applications.

A mesh can then be manufactured by expanding a metal sheet or coil of appropriate thickness at an expansion factor of 10 times or more, preferably 15 times or more. Useful meshes can also be prepared when the metal sheet is expanded by a factor of up to 30 times its original area. Even for annealed valve metals with elongations greater than 20 percent, expansion factors greater than 30:1 will cause the prepared mesh strands to break.
On the other hand, expansion factors less than about 10:1 leave behind wasted metal that does not increase cathodic protection. Further in this regard, expanded meshes must have a void area of 80 percent or more for reasons of cathodic protection efficiency and economy. The porosity of the expanded metal mesh is most preferably about 90 percent or greater, and can be as high as 92 to 96 percent or more while still providing sufficient metal and economical current distribution. With such porosity, the metal strands can be connected at a large number of nodes to provide a margin for the current carrying path through the mesh, thereby preventing individual strands from breaking in large numbers, e.g. during installation or use. The current distribution through the mesh remains useful even when Within the aforementioned expansion factor range, the preferred margin for such metal strands is to provide a network of interconnected strands with approximately 500 to 2000 nodes per square meter of mesh. A number of nodes in excess of about 2000 nodes per mesh square meter is uneconomical. On the other hand, the number of interconnected nodes per square meter is approximately 500.
If it is less than that, the margin of mesh will be insufficient.
With a mesh weight range as described above and a sheet thickness of about 0.05-0.125 centimeters, it is expected that the strand width will be about 0.05 centimeters to about 0.20 centimeters. For special applications in concrete cathodic protection, the total surface area of the interconnected metals, i.e. the combined surface area of the strands and nodes, is approximately 10% of the area covered by the metal mesh.
% to about 50%. It will be appreciated that since this surface area is the total area contributed by all four sides of the square cross-section strand, it can be much greater than 10% of the mesh area even when the porosity is 90%. This area is generally referred to as "metal surface area" or "metal surface area" in this application. The surface area of the metal is approximately 10
If less than 1%, the resulting mesh becomes brittle and harmful fractures occur. On the other hand, if the surface area of the metal exceeds about 50%, the metal will be wasted without any enhancement of corrosion protection.

The mesh obtained after expansion can be easily rolled into a coil for storage or transportation or further manipulation. Typical titanium valve metal has an inner diameter of 20 cm or more and an outer diameter of
Rolls with hollows of up to 150 cm, preferably 100 cm can be prepared. When the mesh is prepared in lengths ranging from about 40 to about 200 meters, preferably up to 100 meters, the mesh can be suitably rolled into a roll. In the case of titanium metal, this roll has a weight of approximately 10-50 kg, but for ease of handling it is usually less than 30 kg, especially when handled outdoors for subsequent coating and cathodic protection work. be.

In valve metal meshes that have been expanded to a large extent in this way, it is most typical that the pores of the mesh have a diamond-shaped hole shape. Such "diamond-shaped" holes feature a long way of design of about 4 cm, preferably about 6 cm to about 9 cm.
LWD) (longer LWDs are also contemplated) and a design short of about 2 cm, preferably about 2.5 to about 4 cm.
design: SWD). For cathodic protection applications in concrete, diamond dimensions
If the LWD exceeds about 9 centimeters, the strands will break causing undesirable voltage losses. In this preferred application, SWDs less than about 2 centimeters or LWDs less than about 4 centimeters are uneconomical, expending too much metal for the desired cathodic protection.

Referring to FIG. 1 in further detail. One diamond shape from a sheet with multiple diamond shapes is generally designated 2. This shape is formed from strands 3 joining at nodes 4. As shown in FIG. 1, the strands 3 and the connecting portions 4 form a diamond hole with a design length in the horizontal direction. When referring to the surface area of interconnected metal strands, e.g. when referring to such surface area being less than about 10 percent of the total measured area of said expanded metal, such surface area is the sum of the strands 3 and connections 4. It is the total area around it. For example, in a strand 3 of square cross section, its surface area is four times the area shown on one side in the drawing. That is, although the strand 3 and its connecting portion 4 are shown thinly in FIG. 1, they easily contribute 20 to 30 percent to the overall measured area of the expanded metal. The "area of the mesh" in FIG. 1, for example, the area in square meters of the mesh, as used in this application, means the area inside an imaginary line drawn around the mesh.

The inner region of the diamond in FIG. 1, that is, the region inside the strand 3 and the connecting portion 4, is referred to as a "diamond hole" in this application. This is an area that has an LWD length and an SWD length, and is also referred to as a ``void'' for convenience, or when the sum of such an area and the metal area around the void is taken as a standard, it is referred to as ``porosity ( void
fraction). As pointed out in FIG. 1 and in the foregoing discussion, the metal mesh used herein has extremely high porosity. Although the shape shown is a diamond shape, many other shapes can be used to achieve extremely high porosity, such as a scallop shape or a hexagon.

Referring to FIG. 2, several individual diamonds 21 are formed from individual strands 22 and their interconnections 25, thereby providing diamond-shaped holes. An example diamond 21 is placed at the interconnection 25 of the strand 22.
It is joined to a metal strip 23 that runs along the diamond-shaped LWD. This assembly is held together with spot welds 24 and strips 2
Each strand joint (node) 25 below 3 is welded by spot welding 24. A commonly used welding technique is electric resistance welding, which is the simplest and most economical spot welding technique. However, other similar welding techniques, such as roller welding, are also conceivable. This weld provides a rigid interconnection between strip 23 and strand 22 with good electrical conductivity. As can be seen with reference to FIG. 2, the strands 22 and connections 25 can have a substantially planar shape. As used herein, the term "substantially planar shape" refers to mesh sheets, especially large ones, which are typically coiled or rolled for storage or handling; ” means capable of being unrolled into a state or shape, i.e. a substantially flat configuration. Furthermore, the connecting part 25
is twice the strand thickness so that its substantially planar or planar shape has a rigid connection when unwound flat.

Referring now to the enlarged view of FIG. 3, it can be seen that the nodes have a thickness 2T, which is twice the thickness of the strands. That is, each strand is approximately
It has a lateral depth or thickness not exceeding 0.125 centimeters and a faciry width (W) of between about 0.20 centimeters.

This expanded metal mesh can be coated with useful coatings. The mesh can also be coated before taking the mesh form, or a combination is also useful. Both coatings before and after the mesh form are useful for loading the catalytically active component onto the substrate and thereby forming the catalytic structure. A feature of catalyst use is that the mesh substrate provides an anode structure with a catalyst coating.

The metal, including the coiled metal mesh, is subjected to one or more various pretreatments prior to the electrocatalyst coating operation. This pretreatment is simple, such as simple immersion. It is not uncommon for the mesh to become surface contaminated with oil or other substances, such as from expansion operations. Pretreatment therefore often includes a solvent degreasing operation. This operation is accomplished with chlorinated and/or fluorinated solvents such as typical halogenated hydrocarbon agents such as chlorotrifluoromethane, methylene chloride, and perchloroethylene. Other coiled metal mesh pretreatments include more typical techniques such as pickling and etching and dry honing or sandblasting. In dry honing, extremely finely divided hard particles in the form of grit are blasted at high speed onto a coiled mesh. A typical etching operation typically involves contacting the metal mesh with an aqueous inorganic acid solution by spraying or dipping. In general, strong aqueous inorganic acids such as hydrochloric acid up to about 30% strength or higher can be used. The use of combination pretreatment techniques is also conceivable. For such combined operations, it is useful not only to combine two different steps in a single operation, such as combining spraying and soaking techniques for degreasing, but also to combine cleaning or soaking with a gentle abrasive treatment. It also includes. If several pretreatment operations are used, for example degreasing and etching, intermediate steps between each operation, such as drying and/or soaking, are also used.

Valve metal from a typical expansion operation is best prepared by first degreasing in a commercially available degreaser containing a boiling halogenated hydrocarbon solvent, such as perchlorethylene, and then etching. This etching consists of contact with a concentrated aqueous hydrochloric acid solution for a period of up to about 20 minutes, such as by dip coating contact. Contact for longer than approximately 20 minutes may result in harmful levels of metal loss during the etching operation. Typically, immersion of the coiled metal mesh in the etching solution for about 5 minutes or more will provide a metal surface with sufficient roughness to enhance coating adhesion and distribution. Concentrated hydrochloric acid solutions containing acid ranging from about 5 to about 30 percent are useful.

The liquid coating composition used is one that provides an electrochemically active coating that is useful in lightweight coatings. This lightweight or “low loading” coating is
The coating provides a coating weight of less than about 0.5 grams of platinum group metal per square meter of metal mesh substrate.
On the other hand, coatings in which platinum metal is present in as little as about 0.05 grams per square meter of metal mesh may also be useful. Typical examples of electrochemically active coatings are platinum or other platinum group metals, but may also be active oxide coatings such as platinum group metal oxides, magnetite, ferrite, cobalt spinel or mixed metal oxide coatings. Such coatings have typically been developed for use as anodic coatings in the electrochemical industry. Suitable coatings of this type are generally described in one or more of U.S. Pat. No. 3,265,526, U.S. Pat. No. 3,632,498, U.S. Pat. Mixed metal oxide coatings include one or more valve metal oxides and platinum, palladium, rhodium,
Includes mixtures with oxides of platinum group metals or mixtures thereof, including iridium and ruthenium, and mixed oxides of valve metals and those metals. From an economic standpoint, low loading electrocatalyst coatings such as those disclosed in US Pat. No. 4,528,084 are preferred.

Coating the coiled metal mesh may be by any means useful for applying liquid coating compositions to metal substrates. Such methods include the immersion spin method and the immersion drain method. Additionally, spray application and combination techniques such as a combination of dip drain and spray application may be used. For such coating compositions to apply electrochemically active coatings, a modified dip-drain method of coiled metal mesh may be most useful. This method involves immersing the coil in a bath of coating composition such that the axis through the hollow center of the coil is at least substantially parallel to the surface of the liquid coating composition. Immersion of the coil in the coating composition may be partial or complete. Preferably, the coil is rotated about its central axis during contact to ensure complete and uniform distribution of the liquid coating composition on the metal substrate. Particularly when coating large rolls of coiled metal, this method is advantageous because the coil is not only partially immersed in the coating solution, but is subsequently rotated so that the coating composition completely wets the mesh substrate. It's a method. To enhance this coating operation, the coil is dipped into the coating composition bath, rotated, pulled out, dipped again, rotated or counter-rotated, and repeated until the coiled mesh is completely coated. It is. Alternatively, the hollow center of the coil may be vertically immersed in the coating composition, either partially or completely, ie, until the entire coil is immersed. After any of the foregoing coating procedures, the coil is removed from the liquid coating composition and the wet coil is simply drained or subjected to other post-coating treatments such as forced air drying.

Cure conditions for electrocatalytic coatings include cure temperatures of about 300°C to about 600°C. Cure times vary from a few minutes to over an hour for each coating layer. For example, curing after several layers of coating takes a long time. The curing operation can be any operation used to cure a coating on a metal substrate. That is, an oven cure including a conveyor oven can be used. Furthermore, infrared cure technology is also useful. For most economical curing, the use of oven curing is preferred and the curing temperature will be in the range of about 450°C to about 550°C. At such temperatures, the cure time will be on the order of several minutes for each coating layer, such as about 3 to 10 minutes.

The greatly expanded coil, although lightweight, also proved difficult to handle because the mesh edges were sharp and dangerous to handle by hand. This coating is therefore particularly advantageous in that it reduces the risk of manual manipulation of the coiled mesh. This coating is useful to make the coil easier to handle when placing it for storage, removing it, or subjecting it to subsequent operations. The application of electrochemically active lightweight coatings is particularly desirable since the coatings do not interfere with subsequent electrical resistance welding. That is, the coating operation described above is used after the coiled mesh has been produced, so that the coated article obtained can not only proceed to the next processing operation, but also be easily manipulated by hand during such operation. Be able to handle it.

When using coiled meshes, it is often desirable to secure additional metal members to the mesh, such as after coating. For example, a metallic current distribution member can be metallurgically bonded to the coated coil. The attachment of additional metal parts can be carried out subsequent to the coating operation. Although various metallurgical joining techniques are possible for the assembly of the coated roll and additional metal elements, electric resistance welding has been found to be efficient. That is, if the additional metal elements include current distribution members, these current distribution members may consist of unwound mesh with strips affixed thereto, and the strips may be spot welded to nodes of the mesh. Furthermore, in such an assembly, the electrocatalyst loading of the current distribution member may be low. Electric resistance welding is well suited for the preparation of this coated metal assembly and can be successfully used even when the metals to be welded in flush contact are each coated. The current distribution member is then connected to a current conductor outside the concrete environment, and the current conductor outside the concrete does not need to be coated. For example, in the case of a concrete bridge deck,
This current distribution member is a rod that extends through the hole and below the floor surface where the current conductor is placed. Thus, all mechanical current connections are made external to the final concrete structure, thereby facilitating access and servicing when needed. Connections of the current distribution rods outside the concrete are made by conventional mechanical means, such as bolt-on shell plate connectors.

Applying the coated mesh for corrosion protection of concrete floors or foundations is simple. A greatly expanded valve metal mesh (hereinafter sometimes simply referred to as "anode") with a suitable electrochemically active coating is unrolled onto such a bed or foundation. The means for fixing the mesh to the foundation may be any means useful for bonding the metal mesh to the concrete without impairing the properties of the mesh as an anode. Typically, non-conductive retaining members are useful. From the point of view of economy, such retaining members are advantageously made of plastic in the form of nails or studs. For example, plastics such as polyvinyl halides and polyolefins are useful.
These plastic retainers are inserted into holes drilled into the concrete. Such a holder has an enlarged head which holds the mesh strand under the head and keeps the anode flat. Alternatively, the retainer may be provided with a partial groove to grip the strand of mesh directly above the drilled hole in the concrete.

Typically, an ionically conductive overlay is used to completely cover the anode structure when the anode is planar and held in intimate contact with the concrete foundation by a retainer. Such an overlay further strengthens the contact between the anode and the concrete foundation.
Ionically conductive overlays that can be used for this purpose include Portland cement and polymer modified concrete.

In a typical operation, the anode can be overlaid with about 2 to about 6 centimeters of Portland cement or latex modified concrete. If a thin overlay is particularly desired, the anode is generally covered with about 0.5 to about 2 centimeters of polymer modified concrete. The expanded valve metal mesh based anode also has the added benefit of being a metal reinforcement, thereby improving the mechanical properties and service life of the overlay. It is also contemplated to use the metal mesh anode structure with materials well known in the art of repairing basic concrete structures such as bridge decks and support columns, and/or using methods well known in the art of repairing such structures.

The following examples illustrate how the invention may be practiced. However, this should not be construed as limiting the present invention.

Example 1 Width 100 centimeters (cm) x length 300 cm x thickness (T) 0.889 millimeters (mm), thickness 0.0635 cm
A non-porous sheet of grade I titanium having an elongation of 24 percent at 68 DEG C. (2-inch) sheet over 0.025 inch (0.025 inch) was expanded into a diamond shape. The die that punched the sheet also functioned as a forming die that expanded the punched slit into a diamond-shaped opening. This method used a punch with an alignment feature on one side to complete the design. Each diamond is 7.62cm
It was LWD x 3.38cmSWD. Expansion ratio is 19:1
For example, a 160 cm long test sheet was expanded to approximately 30.5 m during shaping, and the porosity was 95%. Final strand dimensions are 0.889mm (T) x
It was 0.914mm (W). Expansion is 220 strokes/
The strands did not break. The weight of the final expanded titanium is 0.20 kilograms (Kg) per square meter (m ² ) of mesh obtained, and the actual metal surface area (strands + nodes) is 0.23 m per square meter (m 2 ) of mesh obtained. It was ² . This 30.5 m long mesh was stored and handled in a roll form for convenience.

30cm x 38 pieces of ivy cut from the unrolled mesh
A current distribution rod was spot welded to one end of the cm expanded titanium piece. The structure was then degreased with perchlorethylene vapor to 20% by weight
Etched for 5 minutes in HCl solution. After that, it was immersed in water and dried with steam. It was then coated with a mixed oxide of titanium and ruthenium, with a ruthenium content of 0.35 grams per square meter. The anode thus prepared was subjected to accelerated life testing at high current density in 1.0 MH ₂ SO ₄ . 300000 under this condition
(3 x 10 ⁵ ) milliamperes (mA)/m2 the anode will fail after 7.5 hours and 100000 (1 x 10 ⁵ )
At mA/m2, it failed after 82 hours. Extrapolating this result using the known relationship between current density and anode life, the expected life of expanded titanium at a practical current of 100 mA per square meter of metal surface area was over 200 years.

The anode prepared as described above was then placed on a chloride-contaminated concrete block and covered with a 50 mm thick portland cement. A second identical anode was also placed on a chloride-contaminated concrete block and covered with 38 mm thick latex-modified concrete. Visually inspect both structures;
The cement-to-concrete interconnection in the first block and the modified concrete-to-concrete interconnection in the second block were determined to be desirable. From the accelerated life tests described above, the life of the anodes in these blocks was expected to be very long.

Example 2 For a 5 cm (2-inch) sheet 114 centimeters (cm) wide x 1.69 meters long x 0.635 millimeters (mm) thick with an elongation of 24 percent (0.0635 cm (0.025 inch) or more at 68°C) or more A non-porous coil of grade/titanium was expanded into a diamond shape as described in Example 1.
Each unit of diamond shape is 7.62cmLWD×3.38
It was cmSWD. The expansion magnification is 27:1, for example, a 1.69m long test sheet has an expansion ratio of approximately 45.7m when shaped.
m, and the porosity was 96%.
The dimensions of the final strand were 0.635 mm x 0.736 mm. The expansion rate was 220 strokes/min and the strands did not break. The weight of the finished expanded titanium is 0.12 kilograms (Kg) per square meter (m ² ) of the resulting mesh, and the actual metal surface area (strands + nodes) is 0.16 m ² per square meter (m 2 ) of the resulting mesh. Ta.

The expanded metal exiting the expander was easily coiled into rolls. The diameter of the internal hollow area of the obtained roll is approximately 30 cm, and the overall outer diameter is approximately
It was 40cm long. The roll weight was approximately 11.8 kg. A titanium metal tie wire was used to prevent the roll from unwinding during further manipulation. A support rod was passed through the central hollow area of the roll, and the rod was extended beyond each end, marked with a line from the top to each end, and attached to a lifting device. The support rod assembly was then used to lower the roll into a degreaser containing boiling perchlorethylene solvent. The roll was held in the upper steam zone for approximately 20 minutes. Thereafter, the degreased coil was again immersed in a 20 weight percent aqueous hydrochloric acid solution for 10 minutes using the support rod assembly. This hydrochloric acid aqueous solution
It was maintained at 95°C. After this etching operation, remove the coil from the etching solution and dry it for approximately 15 minutes.
It was soaked in water for a few minutes and then steam dried for about 20 minutes.

To apply an electrochemically active coating onto the coil, the coil was again dipped into the coating solution bath by means of the support rod assembly. A coating solution such as this bath is described in Example 1 of US Pat. No. 3,632,498.
Since the depth of the coating solution was smaller than the coil diameter,
The coil was rotated slowly to expose the entire coil to the coating solution. The coil was then lifted out of the solution, rotated slightly around the support rod, dipped back into the coating solution, and rotated again in the solution. The coil is finally removed from the coating solution, gently shaken by hand, and then held over the coating solution tank for approximately 30 minutes to drain the solution temporarily held in the corners of the diamond-shaped unit, while at the same time removing the coil from the coating solution. was dried.

The dried coil was maintained on the support rod arrangement, which was then used to introduce the coil into a conveyor oven. The coil passed through the furnace in 4 minutes, whereby the temperature of the wire mesh facing the hollow area of the coil reached approximately 500°C. After taking it out of the oven,
Passed through the oven again for 4 minutes. After the second pass, the coil was cooled. The coil was then unwound, but there was no strand breakage or mutual adhesion of adjacent strands due to such coating or curing operations, and the coil could therefore be easily and completely unwound.

The coated coil was unwound, a specimen was cut and analyzed, and the coating was found to be a mixed oxide of titanium and ruthenium, with a ruthenium content of 0.35 grams per square meter. Furthermore, such coatings were found to be well distributed in all randomly selected areas to be analyzed for the desired coating content. Anodes prepared from randomly selected samples and subjected to accelerated life tests were
All of them were shown to have sufficient reinforcement performance for cathodic protection of steel-reinforced concrete and other materials. Coating and curing using a coiled mesh is determined to be a highly desirable method for providing a coating mesh that can be used in such anodes.

Examples of meshes that have been or could be useful are presented below.

Mesh Specifications Type 1 Mesh Composition Titanium Grade 1 Roll Width 112.5cm (45 inches) Length 75-150m (250-500ft) Weight 11.7Kg/ ^100m2 (26lbs/ ^1000ft2 ) Diamond Dimensions 7.6cmLWD x 3.3 cmSWD (3″LWD x 11/3″SWD) Length resistance 0.086 ohm/m (112.5 cm/45 inch width) (0.026 ohm/ft) Width resistance including current distribution 0.02 ohm/m (0.007 Ohm/
ft) Bend radius 0.24 cm (3/32 in) Mesh face bend radius 15 m (50 ft) Type 2 mesh composition Titanium Grade 1 Roll width 122 cm (4 ft) Length 75 to 150 m (250 to 500 ft) Weight 20.2 Kg/ ^100m2 (45lbs/ ^1000ft2 ) Diamond Dimensions 7.6cmLWD x 3.3cmSWD (3″LWD x 11/3″SWD) Length Resistance (122cm, 4ft Width) 0.046ohm/m
(0.014 ohm/ft) Width resistance including current distribution section 0.016 ohm/m (0.005 ohm/ft)
ft) Bending radius 0.24 cm (3/32 in.) Bending radius at mesh face 15 m (50 ft) When coated metal mesh is used for cathodic protection, such as corrosion retardation in steel-reinforced concrete, the mesh is connected to a current distribution member. be done. Such members are generally valve metals, preferably alloys or intermetallic mixtures of the same metals used exclusively in expanded valve metal meshes. This current distribution member must be firmly fixed to the metal mesh. One preferred method of securing the member to the mesh is electrical resistance welding, such as spot welding. Furthermore, welding can be carried out over the coating. That is,
A coated current distribution strip can be placed on a coated mesh with the coated surfaces in contact with each other and welding will still proceed easily. The strips can be spot welded at every node of the mesh, thereby distributing the current evenly.
Placing such current distribution strips every 30 meters along the mesh will normally be sufficient for current distribution.