Abstract: Sacrificial anode assemblies have the advantage that they can provide galvanic protection to steel in concrete and do not require long term maintenance of a DC power supply. However sacrificial anode assemblies often loose adhesion to the concrete surface. This invention discloses the use of a sacrificial anode (4) and a backfill (3) and a tape (5) and an adhesive to protect steel (8) in concrete. The backfill is preferably placed in a shallow cavity (1) in the concrete surface (2) and the sacrificial anode is inserted into the backfill. The cavity is covered with a tape that extends over the adjacent concrete surfaces on opposite sides of the sacrificial anode and backfill and the tape is attached to the concrete surface with the adhesive. The tape and the adhesive holds the anode in place and prevents a weathering environment from damaging the backfill.

Abstract: A single anode system used in multiple electrochemical treatments to control steel corrosion in concrete comprises a sacrificial metal that is capable of supporting high impressed anode current densities with an impressed current anode connection detail and a porous embedding material containing an electrolyte. Initially current is driven from the sacrificial metal [1] to the steel [10] using a power source [5] converting oxygen and water [14] into hydroxyl ions [15] on the steel and drawing chloride ions [16] into the porous material [2] around the anode such that corroding sites are moved from the steel to the anode restoring steel passivity and activating the anode. Cathodic prevention is then applied. This is preferably sacrificial cathodic prevention that is applied by disconnecting the power source and connecting the activated sacrificial anode directly to the steel.

Abstract: An active cathodic protection system, the apparatus comprising a rectifier element with at least one electrical connection to a source of electrical current, the rectifier element associated with a direct current positive (+) output terminal for electrical connection of via an anode connector to a consumable anode, a direct current negative (?) output terminal for electrical connection via a cathode connector to the structure to be protected, grounding means for electrical grounding of the apparatus and anti-cross connection means for preventing the continuing flow of electrical current when the anode connector is associated with the negative output terminal and the cathode connector is associated with the positive output terminal. The cathodic protection system also includes a microprocessor controlled device for shutting the system if an improper current is sensed.

Abstract: Disclosed is a method for the cathodic protection (KKS) of the reinforcements of ferroconcrete edifices against corrosion. According to said method, a) one side of the structural joints of the concrete supporting elements is sealed, b) the KKS anodes are introduced into the structural joints, c) an ionically conductive gel is introduced into the joints that are closed on one side, and d) the structural joints are optionally sealed as a whole. Surprisingly, the required electrical conductivity can be reliably ensured during the entire application period with the aid of the ionically conductive gel, which is a prerequisite for effectively and reliably protecting the steel reinforcements of concrete structures against corrosion.

Abstract: The galvanic cathodic protection of reinforced concrete structures such as bridges, buildings, parking structures, piers, and wharves, is enhanced by the use of an inert water absorbent solid. The absorbent solid and chemicals are mixed with a cementitious binder to form an activating matrix. This matrix surrounds a sacrificial metal anode such as zinc, or aluminum or their alloys. The metal anode is electrically connected to the ferrous reinforcing member by a metallic conductor. The water absorbent solid may be a clay such as bentonite or a hydrated mineral such as vermiculite. It is preferably in the form of discrete particles dispersed throughout the binder. The inclusion of the absorbent solid in the activating matrix serves to increase the protective current, thereby reducing corrosion of the reinforcing components of the concrete structure.

Abstract: Mixed-metal-oxide (MMO) coated precious-metal tape is installed directly on concrete surfaces using an electrically conductive adhesive, thereby obviating the need for slots, holes, cementitious grout or additional concrete. The electrically conductive adhesive is preferably formed by disposing mixed-metal-oxide (MMO) coated precious-metal particles in an adhesive layer. The tape anodes may be installed on the concrete surfaces including a shallow concrete cover or congested reinforcing steel without developing an electrical short circuit between the anode and the reinforcing steel. Overall the invention provides for quick and low cost installation on many concrete structures. Interconnections between the tape anodes and bare metal distribution elements may be made with conductive adhesive or spot welding.

Abstract: Corrosion of steel in a concrete structure such as a column in sea water occurs primarily at the zone which is subject to a wetting and drying action and is inhibited using cathodic protection by attaching to the column at the zone an impervious sealed sleeve which carries no anode itself but which cooperates with an anode body in the water. The sleeve acts to inhibit permeation of oxygen through the concrete to the steel and at the same time acts to promote transfer of current from the anode through the concrete under the sleeve by preventing drying by preventing moisture escape. An anode arrangement may be provided only at the top of the sleeve to consume oxygen in that area. The sleeve may be applied over a layer of grout. The top edge surface of the grout may be sealed from the sleeve to the column.

Abstract: The deterioration of reinforced concrete structures by galvanic corrosion adversely affects roads, bridges, parking garages and buildings that use reinforcing steel in their construction. Galvanic cathodic protection is typically provided for such reinforced concrete structures using embedded sacrificial anodes, such as zinc, aluminum, and alloys thereof. Disclosed herein is an anode assembly (10) for cathodic protection of a reinforced concrete structure. The assembly comprises at least one sacrificial anode member (12). The anode member is covered with an ionically-conductive covering material (14) into which is bound an electrochemical activating agent at least partly covering the sacrificial anode member. One side (26) of the ionically-conductive covering material is configured to conform closely to a steel reinforcing bar. The conforming side has a non-conductive barrier (16) as an integral part of the covering material.

Abstract: A semi-permanent reference electrode for use in monitoring and measuring metals in field applications, such as cathodic protection. This electrode has an outer electrode body with a cap and porous plug. The outer electrode body is filled with a fill solution which is a saturated salt solution formed from a solid salt. The solid salt is hygroscopic with a low deliquescence point. An opening is provided in the cap to allow moisture into the outer electrode body to combine with the fill solution to maintain the saturated salt solution in the field. This saturated salt solution must maintain a constant pH for use in the semi-permanent reference electrode. A wire is used within the outer electrode body which connects to a voltmeter. This voltmeter measures the potential difference between the reference electrode and the field component of interest, which can include pipelines, storage tanks and bridges.

Abstract: The installation and use of embedded sacrificial anodes to protect reinforced concrete may be improved. In one example a cavity [2] is formed in the concrete [3] and a puttylike backfill [4] is placed in the cavity and a compact discrete anode comprising a sacrificial metal element [1] is inserted into the backfill and a space is provided into which the backfill may move when subjected to a pressure arising from the formation of voluminous sacrificial metal corrosion products and a high current is passed from the anode to the steel in the concrete to arrest steel corrosion and activate the anode in the backfill. The space may be provided by venting the backfill to space outside the cavity through an opening [5] or by including a void space within the backfill [6] or a void space within the cavity [7].

Abstract: Corrosion of steel in a concrete structure such as a column in sea water occurs primarily at the zone which is subject to a wetting and drying action and is inhibited using cathodic protection by attaching to the column at the zone an impervious sealed sleeve which carries no anode itself but which cooperates with an anode body in the water below the sleeve. The sleeve acts to inhibit permeation of oxygen through the concrete to the steel and at the same time acts to promote transfer of current from the anode through the concrete under the sleeve by preventing drying by preventing moisture escape. An anode arrangement may be provided only at the top of the sleeve to consume oxygen in that area. The sleeve may be applied over a layer of grout. The top edge surface of the grout may be sealed from the sleeve to the column.

Abstract: There is disclosed a cathodic protection system of reinforced concrete structures with discrete anodes obtained starting from a corrugated planar substrate welded to a longitudinal current collector. The anodes of the invention are particularly suitable for being installed rolled in cylinders, with their axis parallel to the current collectors, positioned inside holes made in the concrete of the structure to be protected.

Abstract: A method of protecting steel in concrete is disclosed. It consists of connecting the steel (6) to a discrete sacrificial anode assembly (7) comprising a base metal (1), a relatively small quantity of catalytic activating agent in contact with the base metal and a substantially inert porous layer (3) that surrounds the base metal and catalytic activating agent. The inert porous layer efficiently maintains a sustainable concentration gradient of the catalytic activating agent between the base metal and the surrounding environment as a result of the electric field across this layer. The preferred porous layer comprises a material that exhibits a net repulsion of negative ions from its pore system and the preferred catalytic activating agent comprises doubly charged sulphate ions as small electric fields maintain very high concentration gradients of these ions resulting in high concentrations at the base metal surface and insignificant concentrations at the assembly periphery.

Abstract: A method is described for preventing and comabating corrosion on semi-dry, moist and wet concrete marine structures, comprising that, against the surface of the structure to be protected on a permanent basis, there is fastened an inert, conductive material, pressed by the fastening against an intermediate contact-establishing, hydroscopic material, and where a voltage is applied on a permanent basis between the reinforcement in the concrete and the affixed inert, conductive material.

Abstract: The present invention provides a curable cathodic corrosion protection powder coating, which comprises a thermosetting resin, a zinc borate compound, a curing agent in an amount effective to cure the coating. Further, the present invention also provides a method of cathode corrosion protection which includes the steps of subjecting the substrate to a mechanical treatment, applying to said treated steel surface, the cathodic protective coating, and polarizing the coated material as a cathode.

Abstract: A cathodic protection system for protecting an underwater structure includes a plurality of blocks which are capable of conforming to various structures. Each of the blocks include: a flexible wire rope, the rope constructed and arranged to pass through the center of each block in two directions, and embedded therein to fasten the blocks to each other by rows and columns; a sacrificial anode embedded in at least one of the blocks, and electrically attached inside the block to the flexible wire rope; and a connecting system electrically attached to the wire rope and to the underwater structure. Each block has a non-abrasive pad attached to it. The pad provides spacing between the block and the underwater structure. The system includes means for collecting performance data from the system. The sacrificial anode is made of a composition taken from the group comprising alloys of: zinc, aluminum, or magnesium.

Abstract: An apparatus, system, method and computer program product directed to controlling corrosion of a conductive structure in contact with a corrosive environment and electrically connected to one or more anodes, wherein the anodes are less noble than the conductive structure, where the corrosion is controlled by a controllable filter and a corresponding electronic control unit configured to process at least one stored or measured parameter, and wherein the apparatus, system and method serve to prolong the lifetime of the one or more anodes by reducing, minimizing or substantially eliminating their sacrificial character.

Abstract: A method for protecting metal-containing structures, in particular electrically conductive structures, deposited on a substrate, against corrosive attacks, in particular electrocorrosion attacks. The method applies at least temporarily to the structure a passivation electric voltage in the passivation range of the conductive material concerned.

Abstract: Cathodic protection of a structure including a steel member at least partly buried in a covering layer, such as steel rebar in a concrete structure, is provided by embedding sacrificial anodes into the concrete layer at spaced positions over the layer and connecting the anodes to the rebar. The anode body is formed, by pressing together finely divided powder, flakes or fibers of a sacrificial anode material such as zinc to define a porous body having pores therein. The sacrificial anode material of the anode member is directly in contact with the covering material by being buried or inserted as a tight fit into a drilled hole so that any expansion forces therefrom would be applied to the concrete with the potential of causing cracking. The pores are arranged however such that corrosion products from corrosion of the anode body are received into the pores sufficiently to prevent expansion of the anode body to an extent which would cause cracking of the covering material.

Abstract: Cathodic protection of steel in a building or other concrete or similar structure is provided by locating an anode in a suitable location adjacent to the steel and providing an impressed current from a power supply to the anode. The anode is formed from a material which is more electro-negative than the steel so that in the event that the power supply falls below the galvanic potential therebetween, current flows under galvanic action to replace the impressed current. A diode in the circuit prevents flow of current across the power supply but allows the galvanic current when the power supply fails open circuit. An additional diode can be provided in the event the power supply fails closed circuit to prevent reverse current flow.

Abstract: A method for managing corrosion of an underground structure includes placing an anode in the ground and electrically connecting it to the underground structure. Access to the ground is obtained through a container at least partially buried in the ground, such that the surface of the ground proximate the container does not need to be penetrated in order to position the anode. A hole is bored through a wall of the container to access the ground proximate the container. Material is removed from the ground to provide a location for the anode. The anode is placed in the ground and backfilled with an electrically conductive backfill. A wire leading from the anode is then terminated inside the container at an electrical connection with another electrical conductor connected to the underground structure. The lid is replaced on the container, and the entire process is performed without penetrating the surface of the ground proximate the container.

Abstract: Cathodic protection of an existing concrete structure, including a steel member at least partly buried, such as steel rebar, in the concrete structure, is provided by embedding anodes into a fresh concrete layer applied over an excavated patch and/or as a covering overlay. The anodes are embedded at spaced positions or as an array in the layer and connected to the rebar. A reinforcing layer is applied to the anode or adjacent the anode to resist expansion of the anode body tending to cause cracking of the concrete caused by the larger volume of the corrosion products relative to the anode material. Pores are provided in the anode body so as to take up the corrosion products. The reinforcing layer can be provided in the actual anode body as a closed surface surrounding the anode material inside or may be provided in the concrete as a layer on top of the anode in an array form at or near the outer surface of the concrete.

Abstract: First and second axial current meters (ACM) are mechanically connected to a well casing just above and below a corrosive zone and a master axial current meter (MACM) is connected to the casing at the earth's surface, the MACM periodically obtaining measurements of axial current from the ACMs to determine how much cathodic protection current is to be applied to the casing to avoid corrosion.

Abstract: An active cathodic protection system, the apparatus comprising a rectifier element with at least one electrical connection to a source of electrical current, the rectifier element associated with a direct current positive (+) output terminal for electrical connection of via an anode connector to a consumable anode, a direct current negative (?) output terminal for electrical connection via a cathode connector to the structure to be protected, grounding means for electrical grounding of the apparatus and anti-cross connection means for preventing the continuing flow of electrical current when the anode connector is associated with the negative output terminal and the cathode connector is associated with the positive output terminal.

Abstract: Systems and methods of cathodic protection. The system includes a metallic housing, a backplane situated within the metallic housing, a cathodic protection card coupled to the backplane and a permanent anode, external to the metallic housing, coupled to the cathodic protection card through an isolated port. The cathodic protection system is powered using span power. The permanent anode and metallic housing are adapted to form a closed circuit when both come in contact with an electrolyte. The permanent anode is maintained at a higher potential than the metallic housing.

Abstract: The cathodic protection system of a concrete structure (22) uses sacrificial anodes such as zinc, aluminum and alloys thereof embedded in mortar. A humectant is employed to impart high ionic conductivity to the mortar in which the anode is encapsulated. Lithium nitrate and lithium bromide and combinations thereof are preferred as the humectant. The anode (10) is surrounded by a compressive, conductive matrix (12) incorporating a void volume between 15% and 50% to accommodate the sacrificial corrosion products of the anode. A void space of at least 5% of the total volume of the anode (12) may be provided opposite to the active face of the anode. Synthetic fibers such as polypropylene, polyethylene, cellulose, nylon and fiberglass have been found to be useful for forming the matrix. A tie wire is used to electrically connect the anode to the reinforcing bar.

Abstract: The present invention relates to a method of and an apparatus (20) for cathodic protection of reinforced concrete using discrete anodes (22) in or on the reinforced concrete member (14) to improve performance and service life of the discrete anodes. The discrete anode (22) is embedded in a cementitous grout or mortar (24) to encapsulate the anode (22) and provide contact to complete the cathodic protection circuit. A lithium salt is added to the cementitous grout or mortar (24) in an amount of at least about 0.05 gram per cubic centimeter. The lithium salt functions to enhance the performance of the cathodic protection system (20) by minimizing the deleterious effects of the anode reaction products on the grout or mortar adjacent to the anode and increasing the protective current delivered to the reinforcing steel.

Abstract: A corrosion-inhibited system for providing a utility service to a plurality of consumers includes a plurality of metallic utility service structures, each utility service structure having components buried in a common electrolyte and electrically connected to each other through an electrical utility service connected to an electric utility supply common to each of the consumers in the plurality of consumers. The system further includes a single protection apparatus including at least one anode in physical contact with the common electrolyte. The system further includes a conductor physically connecting the single protection apparatus to only one of the utility service structures.

Abstract: A method to demolish concrete that comprises electrically connecting rebar disposed within the concrete to a power supply, electrically connecting a counter electrode within electro-osmotic communication of the concrete to a power supply, and externally providing electrolyte as supplemental moisture for the concrete. An electric field is created within the concrete and causes water moisture to migrate toward the rebar thereby expediting the corrosion thereof. The corrosion of the rebar generates iron oxides, which because of their greater volume, cause areas of localized pressure within the concrete. As the corrosion process proceeds, an accumulation of oxides increases the localized pressure to cause cracking within the concrete.

Abstract: The present invention provides a method of inhibiting or preventing corrosion of reinforced steel in concrete by eliminating the differences in surface potentials that result in the total pasivation of corrosion activity and create an environment in the steel that does not allow corrosion. The method, optimally includes measuring the active non-uniform surface potential in the steel and passing a DC voltage through the concrete and steel to stop corrosion providing a substantially uniform potential on the reinforced steel. The current is controlled and adjusted to send pre-determined amounts of electrical energy to individual areas targeted for treatment. A corrosion potential survey may be conducted to determine the energy requirements necessary for the corrosion condition or a reference electrode may be strategically placed on the concrete structure.

Abstract: A semiconductor system is provided that uses semiconductive organic polymers, electronics and semiconductor technology to provide a wide array of semiconductor components and a system of preventing corrosion of a surface of a metal structure in contact with a corrosive environment involving: (a) a semiconductive organic polymer coating in conductive contact with at least part of the surface; and (b) an electronic filter for filtering corrosive noise and a method of preventing corrosion using the system.

Abstract: A prefabricated ground mat with cathodic protection adapted to protect persons from induced electrical potentials in a pipe or other electrical conductor buried below a ground-level surface, adapted to protect test stands, valve sites, metering stations, pig launchers and receivers, access portals, or other exposed, above-ground equipment which are electrically connected to the buried conductor, from such electrical potentials, and adapted to protect the buried conductor from oxidation due to the ground grid. Multiple mats may be buried between the underground conductor and the ground-level surface and electrically connected to either the underground conductor, the above-grade buried conductor, or both. The mats are made of materials such that the galvanic cell formed by the electrical union of the underground conductor with the mat cause the mat to be consumed.

Abstract: Cathodic protection of a structure including a steel member at least partly buried in a covering layer, such as steel rebar in a concrete structure, is provided by embedding sacrificial anodes into the concrete layer at spaced positions over the layer and connecting the anodes to the rebar. The anode body is formed, by pressing together finely divided powder, flakes or fibers of a sacrificial anode material such as zinc to define a porous body having pores therein. The sacrificial anode material of the anode member is directly in contact with the covering material by being buried or inserted as a tight fit into a drilled hole so that any expansion forces therefrom would be applied to the concrete with the potential of causing cracking. The pores are arranged however such that corrosion products from corrosion of the anode body are received into the pores sufficiently to prevent expansion of the anode body to an extent which would cause cracking of the covering material.

Abstract: An apparatus, system, method and computer program product directed to controlling corrosion of a conductive structure in contact with a corrosive environment and coated with a semiconductive coating, where the corrosion is controlled by a controllable filter and a corresponding electronic control unit configured to process at least one stored or measured parameter.

Abstract: The present invention provides a curable cathodic corrosion protection powder coating, which comprises a thermosetting resin, a zinc borate compound, a curing agent in an amount effective to cure the coating. Further, the present invention also provides a method of cathode corrosion protection which includes the steps of subjecting the substrate to a mechanical treatment, applying to said treated steel surface, the cathodic protective coating, and polarizing the coated material as a cathode.

Abstract: Cathodic protection of an existing concrete structure, including a steel member at least partly buried, such as steel rebar, in the concrete structure, is provided by embedding anodes into a fresh concrete layer applied over an excavated patch and/or as a covering overlay. The anodes are embedded at spaced positions or as an array in the layer and connected to the rebar. A corrosion inhibitor is added into the fresh concrete at least at the interface and more preferably in admixture with the fresh concrete which acts to reduce the flow of ionic current to the steel or between the anode member and the steel in the fresh covering material without significantly increasing the resistivity of the fresh covering material and without inhibiting the ionic current between the anode member and the fresh covering material. In this way the current to the steel in the existing concrete is maximized to maximize the cathodic protection to the existing steel which is the primary target.

Abstract: A corrosion-inhibited system for providing a utility service to a plurality of consumers includes a plurality of metallic utility service structures, each utility service structure having components buried in a common electrolyte and electrically connected to each other through an electrical utility service connected to an electric utility supply common to each of the consumers in the plurality of consumers. The system further includes a single protection apparatus including at least one anode in physical contact with the common electrolyte. The system further includes a conductor physically connecting the single protection apparatus to only one of the utility service structures.

Abstract: The invention provides a reinforced concrete having improved corrosion resistance in which the content of voids in the concrete at the surface of the steel reinforcement is below 0.8%, preferably below 0.5%, more preferably below 0.2% by area of steel and in which there is a layer of solid alkali, preferably at least one micron in thickness on the steel surface. The reinforced concrete preferably has a chloride threshold level of at least 0.5% preferably at least 0.8% by weight of the cement. The invention also provides a process for reducing corrosion of steel reinforcement in concrete which comprises forming a reinforced concrete in which the voids at the steel surface are below 0.5% by volume and in which there is a layer of solid alkali on the steel surface the layer being at least 1 micron in thickness and covering at least 20% of the steel surface.

Abstract: Coating compositions and methods of their use are described herein for the reduction of corrosion in imbedded metal structures. The coatings are applied as liquids to an external surface of a substrate in which the metal structures are imbedded. The coatings are subsequently allowed to dry. The liquid applied coatings provide galvanic protection to the imbedded metal structures. Continued protection can be maintained with periodic reapplication of the coating compositions, as necessary, to maintain electrical continuity. Because the coatings may be applied using methods similar to standard paints, and because the coatings are applied to external surfaces of the substrates in which the metal structures are imbedded, the corresponding corrosion protection may be easily maintained. The coating compositions are particularly useful in the protection of metal-reinforced concrete.

Abstract: The invention relates to a combination electrode for the restoration of corrosion-damaged reinforced concrete and a method for controlling the same. The combination electrode according to the invention comprises a dimensionally stable electrode (1); a prefabricated, reusable electrolyte reservoir (2); a means for protecting against evaporation (3); a prefabricated, exchangeable, anionic ion exchanger element (4); a central fastener with anchor, anchor rod, and eccentric quick-clamping device (5); a reference electrode (6) on the anchor head; a wetting device (7); a power-switching device for anodic regulation (8); a measuring system for determining the condition on the ion exchanger element (9); as well as electrical connections for the reference cell. The dimensionally stable electrode (1), the means for protecting against evaporation (3), the electrolyte reservoir (2), and the ion exchanger element (4) are thereby connectable to each other in the form of a sandwich construction.

Abstract: Numerical techniques such as the finite element method (FEM) are used to model the current and voltage distribution in concrete structures such as bridges. The geometric arrangement of groundbeds and the ideal locations for the electrical contacts vis-a-vis the geometry of the bridge and the rebars can thereby be predicted and a cathodic protection (CP) system for the bridge designed. A magnetic sensor is used to sense the magnetic field generated by the CP current, and a voltmeter or an oscilloscope to measure the output of the magnetic sensor. A current interrupter is also used to interrupt the CP current at the source. The current is mapped by placing the magnetic sensor on or above the concrete surface. By moving the sensor from one location to another, the current is mapped over the entire structure. To achieve uniform distribution over the entire structure, an “expert” CP system controlled by a variety of current and environmental sensors and a dedicated microprocessor is described.

Abstract: Cathodic protection of a structure including a steel member at least partly buried in a covering layer, such as steel rebar in a concrete structure, is provided by embedding sacrificial anodes into the concrete layer at spaced positions over the layer and connecting the anodes to the rebar. Each anode is inserted into a drilled hole in the layer and is electrically attached to the rebar in the same or an adjacent hole by a steel pin which is attached to the reinforcement by arc welding or by impact. In the arrangement where the anode and the attachment are in the same hole, the pin passes into or through the anode so as to hold the anode rigidly within the hole. The hole is filled by a settable filler material.

Abstract: A grid anode for cathodic protection of steel reinforced concrete structures formed of multiple valve metal strips including multiple electric current-carrying valve metal strips. Valve metal strip grid anodes without an electrocatalytic metal surface can be used in a cathodic protection system operated at an anode current density up to about 20 milliamps per square foot. Composite anodes having an electrocatalytic metal coating are useful at higher anode current densities.

Abstract: A metal anode useful in a galvanic or impressed current cathodic protection system for a steel reinforced concrete article is a unitary, multi-plane, porous, metal anode strip or ribbon having a plurality of louvers defining a plane or planes at the lateral extremities of said louvers. In one embodiment, louvers extending in their long dimension longitudinally on the anode strip are spaced apart from adjacent louver units by an intermediate plane. Louvered anode strips consisting of a valve metal or alloy or mixture thereof are useful at an anode current density of up to about 20 milliamps per square foot. Louvered metal anodes comprising an electrocatalytically active coating on a valve metal substrate are useful at higher anode current densities. Sacrificial metal anodes such as zinc anodes are useful in galvanic cathodic protection systems.

Abstract: The invention provides a reinforced concrete having improved corrosion resistance in which the content of voids in the concrete at the surface of the steel reinforcement is below 0.8%, preferably below 0.5%, more preferably below 0.2% by area of steel and in which there is a layer of solid alkali, preferably at least one micron in thickness on the steel surface. The reinforced concrete preferably has a chloride threshold level of at least 0.5% preferably at least 0.8% by weight of the cement. The invention also provides a process for reducing corrosion of steel reinforcement in concrete which comprises forming a reinforced concrete in which the voids at the steel surface are below 0.5% by volume and in which there is a layer of solid alkali on the steel surface the layer being at least 1 micron in thickness and covering at least 20% of the steel surface.

Abstract: A system for preventing corrosion of a surface of a metal structure in contact with a corrosive environment comprising: (a) a semiconductive coating in conductive contact with at least part of the surface; and (b) an electronic filter for filtering corrosive noise and a method of preventing corrosion using the system.

Abstract: A method of electrochemical treatment of prestressed concrete which comprises supplying a direct current between a steel embedded in the prestressed concrete as a cathode and an anode on the surface or inside of the concrete at a voltage higher than the hydrogen evolution potential, wherein an effective tensile force acting on the PC steel tendon embedded in the concrete is not greater than 80 % of the tensile strength of the PC steel tendon, and a method of electrochemical treatment of prestressed concrete which comprises supplying a direct current between a steel tendon embedded in the prestressed concrete as a cathode and an anode on the surface or inside of the concrete at a voltage higher than the hydrogen evolution potential, wherein the voltage is adjusted to less than the hydrogen evolution potential at least once during electrochemical treatment.

Abstract: A system for preventing corrosion and/or fouling of a surface of a biomedical device in contact with a corrosive environment comprising: (a) a semiconductive coating in conductive contact with at least part of the surface; and (b) an electronic filter for filtering corrosive noise and a method of preventing corrosion and/or fouling using the system.

Abstract: A cathodic protection system for protecting buried conducting structures, subject to corrosion such as well casings, pipe lines and the like, utilizes a plurality of pulsed D.C. current sources with the negative output terminal of each source connected to a separate structure and the positive output terminal of the sources connected to a common anode located near the structures. A control circuit synchronizes the operation of the several D.C. sources and sets the frequency and width of the output pulses. The amplitude of the output pulses from each D.C. source may be separately adjusted.

Abstract: An existing concrete structure is restored by embedding sacrificial anodes into the concrete layer at spaced positions over the layer and connecting the anodes to the reinforcing members to provide a cathodic protection against corrosion. Each anode is inserted into a drilled hole in the layer of sufficient depth to expose the reinforcement. A steel pin passes through a bore in the cylindrical anode and is attached to the reinforcement by arc welding or by impact so as to hold the anode rigidly within the hole. The hole is filled by a settable filler material. In order to maintain effective current conduction from the anode to the reinforcement through the filler over an extended period to maintain the required protection, there is added a material to hold the pH in a preferred range of the order of 12 to 14 and a deliquescent material to absorb moisture into the filler.