Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Metal or metal alloy
Patent
1998-08-07
2000-09-19
Bell, Bruce F.
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Metal or metal alloy
205724, 20419608, 20419604, 2041961, 20419616, 20419618, 2041963, 204280, C23F 1300
Patent
active
06120675&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an electrochemical method and an electrode thereof The invention can be applied to a wide variety of uses. It is particularly effective in the treatment of reinforced concrete. Such concrete comprises a steel bar reinforcing framework swithin a body of set concrete. Other uses will be described below.
BACKGROUND OF THE INVENTION
It is known to connect such framework to a source of direct current to apply a voltage sufficient to maintain the metal in a corrosion resistant state, to avoid or treat corrosion. Such a system is called cathodic protection.
Generally this technique utilises a distributed anode system such as metal mesh, or conductive coatings such as paints and speciality gunited and sprayed material. There are however some areas which cannot be addressed in this way and "discrete" or "point" anodes are suggested. There are already two basic types of point anodes on the market. the most common being a platinised titanium rod. The other type is generally a shaped titanium mesh or titanium metal tube or plate, catalysed with an appropriate or mixed metal oxide based material.
The platinised titanium rod cannot be used alone however, because at the current ratings required (which are controlled by the density of the steel bars in the vicinity), the current density at the anode surface would be very high, generating acid at a rate far faster than it could diffuse away (and ultimately be neutralised by the alkali generated on the cathodic reinforcing bars). Hence the concrete would be destroyed by acid attack in the neighbourhood of the anode. The US National Association of Corrosion Engineers have a guideline that the current density should be no higher than 100 A./m.sup.2 of concrete area to avoid this phenomenon. The rod is usually put in a significantly larger hole (typically 12 mm diameter) than would otherwise be required and the void is filled with a carbon based conductive paste to increase the surface area and hence reduce the current density at the concrete surface. For cost reasons however they still tend to be run well above the NACE guidelines.
At current densities above 0.3 mA.cm length (about 800 mA/m.sup.2) the carbon backfill is consumed by anodic oxidation forming CO.sub.2. As a result the contact between the carbon and the concrete is lost and the voltage to drive the protecting current rises, often outstripping the rating of the rectifier. In addition to this though, other mechanisms are possibly taking place. The high current flows generate gases, typically oxygen with traces of chlorine or carbon dioxide from the oxidation of the carbonaceous paste at the anode surface and this may have difficulty escaping, causing blowholes further reducing the contact at the concrete surface. (It is known that at very high current densities (around 15 Am.sup.2) the anodes can "gas block" within hours of being powered up.)
Generally, because of the need to attend to a specialised conductive carbonaceous grout, the rod is restricted to anodes near the surface. Often there is steel work buried deep within the structure which would be assisted with a local anode close by.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a more convenient and advantageous point electrode for use in the treatment of reinforced concrete and other electrochemical applications.
BRIEF SUMMARY OF THE INVENTION
In one aspect the invention provides an electrochemical electrode for use in electrochemical treatment of reinforced concrete or the like, the electrode comprising a wall comprising a porous material having an external and internal surface, a supply conductor being, in use, in electrical contact with the internal surface and with a supply of electric current.
The wall may be of any appropriate three dimensional shape, typically a cylinder or sphere. Because the connection of the conductor is connected to the internal surface of the wall anodic corrosion is avoided. The external surface will be corrosion resistant.
The wall is preferably sh
REFERENCES:
patent: 2863819 (1958-12-01), Preiser
patent: 3038849 (1962-06-01), Preiser
patent: 4486288 (1984-12-01), Linder
patent: 4710644 (1987-12-01), Baach
patent: 4872957 (1989-10-01), Dong et al.
patent: 4966675 (1990-10-01), Steininger
patent: 5141607 (1992-08-01), Swiat
WPI Accession No. 79-20713 B/11--Abstract--JP 54015475 (Mitsubishi) no month/year available.
WPI Accession No. 79-766640 B/42--Abstract--SU 643551 (Nasonov) no month/year available.
Hayfield Peter Charles Steele
Hill Andrew
Atraverda Limited
Bell Bruce F.
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