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Topic: Galvanic anodes

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sacrificial anode

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	Galvanic series
		Galvanic series relationships are useful as a guide for selecting metals to be joined, will help the selection of metals having minimal tendency to interact galvanically, or will indicate the need or degree of protection to be applied to lessen the expected potential interactions.
		In general, the further apart the materials are in the galvanic series, the higher the risk of galvanic corrosion, which should be prevented by design.
		The use of the galvanic series has to be done with caution and a basic knowledge of the environments that is a necessary part of this serious form of corrosion.
	www.corrosion-doctors.org /Definitions/galvanic-series.htm (646 words)

	Galvanic anode - Wikipedia, the free encyclopedia
		A galvanic anode, also known as a sacrificial anode, is one of the main components of a galvanic cathodic protection system used to protect metals from galvanic corrosion, by the use of a metal electrode which is itself consumed instead in an anodic oxidation reaction.
		This is the galvanic anode: the pipeline is electrically connected at intervals to buried plates of magnesium.
		Galvanization (or galvanizing) is the process of coating steel with zinc, which then forms both a protective layer and a galvanic anode.
	en.wikipedia.org /wiki/Galvanic_anodes (329 words)

	Cathodic protection - Wikipedia, the free encyclopedia
		Galvanic anodes are designed and selected to have a more "active" voltage (technically a more negative electrochemical potential) than the metal of the structure (typically steel).
		The positive DC output terminal is connected via cables to the array of anodes buried in the ground (the anode groundbed).
		For many applications the anodes are installed in a 60 m (200 foot) deep, 25 cm (10-inch) diameter vertical hole and backfilled with conductive coke (a material that improves the performance and life of the anodes).
	en.wikipedia.org /wiki/Cathodic_protection (623 words)

	GoBridges.com - Galvanic corrosion protection systems for concrete bridges
		Six embedded galvanic anodes were installed in each beam end with one in the top flange, one in the web section, and four in the critical bottom flange.
		Galvanic systems obtain their electric current from the corrosion of a sacrificial anode (such as zinc), while ICCP obtains power from a DC supply (often an AC/DC rectifier) distributed to the steel through an inert or longlife anode.
		The anode strips were bonded to the prepared surface with a low-resistance mortar to ensure a conductive path between the anodes and the base concrete.
	www.gobridges.com /article.asp?id=258 (2084 words)

	gbed (Site not responding. Last check: 2007-10-23)
		Anode materials used for underground impressed current systems are generally graphite or high silicon cast iron.
		In the groundbed, it is preferred for the anode to be surrounded by a carbonaceous backfill.
		Anode current density output is generally 100 and 800 Am-2 in ground and seawater respectively.
	www.umist.ac.uk /corrosion/lecturenotes/JDS_Notes/gbed.htm (1108 words)

	Patent 4544465: Galvanic anodes for submergible ferrous metal structures
		This sacrificial anode is individually secured to the structure and thus would have to be replaced after use by a diver descending to the depth at which it is located and welding a replacement anode to the structure at that point.
		This anode comprises an elongated carrier cable which may be secured to the platform to span the space between the submerged legs thereof and carries an elongated anode along the length of the cable intermediate its ends.
		The insulating spacers are positioned where the anode string is in the vicinity of a portion of the submerged structure that does not require the degree of corrosion protection that the welded joints require.
	www.freepatentsonline.com /4544465.html (3123 words)

	CP System Design
		Galvanic Anode: A metal which, because of its relative position in the galvanic series, provides sacrificial protection to metals that are more noble in the series, when coupled in an electrolyte.
		Distributed Anode Groundbed: A group of anodes installed close (5 to 20 feet) to and along a structure to be protected and spaced on 25 to 500 foot centers.
		Galvanic anode installations tend to be used mostly on underground structures in applications where cathodic protection current requirements are small and where earth resistances are acceptably low.
	www.delweg.com /cppapers/cpsystem.htm (1735 words)

	Science Fair Projects - Galvanic anodes
		A galvanic anode is one of the main components of a galvanic cathodic protection system used to protect a metal structure from corrosion.
		Iron has a stronger tendency to corrode then copper and when connected to the hull, the corrosion rate of the copper was dramatically reduced.
		Today, galvanic anodes are made in various shapes using alloys of zinc, magnesium and aluminum.
	www.all-science-fair-projects.com /science_fair_projects_encyclopedia/Galvanic_anodes (396 words)

	Patent 4435263: Backfill for magnesium galvanic anodes
		A magnesium anode backfill composition is prepared by mixing calcium sulfite, bentonite, and at least one compound selected from the group comprising sodium alkylates and sodium dialkyldithiocarbamates, wherein said bentonite contains a substantial amount of alkaline earth metal bentonite, such as calcium-bentonite.
		In contradistinction to sacrificial aluminum anodes, where halide ions in the backfill are often desired to disrupt the passivating effect of Al(OH).sub.3 formed on the Al anode, Mg anodes tend to suffer accelerated and wasted corrosion if halide ions are added to the backfill.
		Preferably, the present backfills are utilized in packaged arrangements, wherein the anode is encompassed in the backfill, whereby the entire package is installed in the ground, wired electrically from the core of the anode to the metal structure to be protected, and water is added to wet (usually saturate) the backfill.
	www.freepatentsonline.com /4435263.html (2476 words)

	Long-Term Effectiveness of Cathodic Protection Systems on Highway Structures, FHWA-RD-01-096
		When anode materials such as zinc are used for impressed-current systems, if they are in contact with the steel, although the system is de-energized, they will form a galvanic couple with the steel and produce currents in the element that impact DC measurements.
		The titanium mesh anode was installed on the entire surface of the tie beam and the footings with the exception of the bottom surface of the footings.
		The arc-sprayed titanium anode was installed on the entire surface of the tie beam and the footings, with the exception of the bottom surface of the footings.
	www.tfhrc.gov /pavement/ltpp/reports/01096.htm (14949 words)

	Sacrificial Zincs
		The most common casualty of galvanic corrosion is a bronze or aluminum propeller on a stainless steel shaft, but metal struts, rudders, rudder fittings, outboards, and stern drives are also at risk.
		The way we counteract galvanic corrosion is to add a third metal into the circuit, one that is quicker than the other two to give up its electrons.
		The mounting bolts for these anodes are connected by heavy-gauge electrical cable to the bonding circuit.
	www.capsante.com /Articles/howto_sacrificial_zincs.htm (885 words)

	Vector Corrosion Technologies: Galvanic Protection
		Galvanic protection systems utilize sacrificial anodes that naturally generate an electrical current to mitigate corrosion of the reinforcing steel.
		Galvashield® XP and Galvashield XP+ embedded zinc anodes are examples of discrete galvanic anodes that are used to provide corrosion mitigation for concrete repair.
		Galvashield CC zinc anodes are installed into chloride contaminated concrete, carbonated concrete or areas with high corrosion potentials to achieve corrosion control in targeted areas of concrete structures.
	www.vector-corrosion.com /galvanic_main.html (208 words)

	HI-AMP Zinc Marine Anodes by Farwest Corrosion Control
		Galvanic efficiency relates directly to the anode's service life.
		For special requirements, HI-AMP anodes for ballast tanks, piers and pilings can be furnished with a wide variety of cores and to the range of dimensions shown in the accompanying table.
		Anodes contain 1/2" diameter straight electrogalvanized steel core rod for direct welding or assembly to two flat bards with "U" bolts as shown.
	www.farwestcorrosion.com /fwst/anodgalv/fed02.htm (825 words)

	FireguardÂ® Installation & Testing Instructions - Divisions of STI/SPFA (Site not responding. Last check: 2007-10-23)
		The types of anodes commonly used are high potential magnesium and high purity zinc, and are typically packaged in a powdered backfill consisting of 75% hydrated gypsum, 20% bentonite clay, and 5% sodium sulfate.
		Anodes may be installed on a "distributed" basis of every 20 to 50 feet, or as a "ground bed" remote from the pipe in "gangs" of 4 to 10 anodes depending upon the current requirements.
		Galvanic Anode: A metal which, as a result of its internal electromotive energy level, provides sacrificial protection to a metal or metals that are more noble (less negative), when coupled in an electrolyte.
	www.steeltank.com /library/pubs/recprac/r89291/r89291.aspx?print=true (10904 words)

	Electrochemistry Encyclopedia --- Electrochemistry of corrosion
		The flow of electrons between the corroding anodes and the non-corroding cathodes forms the corrosion current, the value of which is determined by the rate of production of electrons by the anodic reaction and their consumption by the cathodic reaction.
		The pit is the anode of an electrochemical corrosion cell, and the cathode of the cell is the non-pitted surface.
		This combination of being the anode of a corrosion cell and existing in an acidic, high-chloride environment where repassivation is difficult makes the crevice interior subject to corrosive attack.
	electrochem.cwru.edu /ed/encycl/art-c02-corrosion.htm (4309 words)

	Intro to Corrosion: Practical Application of Cathodic Protection (Site not responding. Last check: 2007-10-23)
		When the proper amount of current flow is discharged from the anodes, it is collected onto the pipe and overpowers the natural corrosion currents that were discharging from the anodic areas and as a result there will be a net current flow onto all areas of the pipe surface.
		In a cathodic protection system utilizing galvanic anodes, advantage of this effect is taken by purposely establishing a dissimilar metal cell strong enough to counteract the corrosion cell normally existing on the pipeline.
		The galvanic anodes used in soil applications are usually made of a magnesium alloy.
	www.commerce.state.ut.us /pubutls/PLScp001.htm (449 words)

	Emerging Construction Technologies
		The palm-sized anode consists of a galvanic zinc core surrounded by an active cementitious matrix.
		These anodes are designed to reduce the ring anode corrosion commonly associated with concrete patch repairs and delay the onset of future corrosion.
		Ring anode corrosion is caused by differences in corrosion potential between areas which have been patched and the remaining portions of the structure.
	cobweb.ecn.purdue.edu /ECT/Civil/galvanic.htm (539 words)

	Galvanic Corrosion
		Galvanic corrosion is frequently referred to as dissimilar metal corrosion.
		Galvanic corrosion can occur when two dissimilar materials are coupled in a corrosive electrolyte.
		The zinc anodes are maintained and replaced as required to insure continued protection.
	www.materialsengineer.com /G-Galvanic-Corrosion.htm (158 words)

	Corrosion Prevention through Cathodic Protection
		The selection of an alloy for a sacrificial anode must be made with consideration for the electrolyte in which the anode and the structure are placed.
		Additional factors are the size and shape of the anode, any protective coating or wrapping applied to the structure, and the intended design life of the system.
		In this type of system, the anodes are installed within the electrolyte around the structure and are connected to the positive output terminal of the rectifier.
	www.cpsolutionsinc.net (500 words)

	HI-AMP Zinc Marine Anodes by Farwest Corrosion Control
		In some cases, the anode's productive life ends before all of the available anode material is consumed.
		For special requirements, HI-AMP anodes for ballast tanks, piers and pilings can be furnished with a wide variety of cores and to the range of dimensions shown in the accompanying table.
		Anodes contain 1/2" diameter straight electrogalvanized steel core rod for direct welding or assembly to two flat bards with "U" bolts as shown.
	www.farwst.com /fwst/anodgalv/fed02.htm (817 words)

	BoatUS.com Seaworthy magazine
		Galvanic corrosion occurs whenever two dissimilar metals are immersed in electrolyte and the metals are connected direct contact or by an external wire.
		As the anodes are worn down, all of the boats’ outdrives vulnerable to galvanic corrosion.
		Galvanic isolators attach to the green grounding wire to limit galvanic current flow (up to about 1.2 volts) between neighboring boats while also allowing dangerous AC current safely pass through to the ground shore.
	www.boatus.com /seaworthy/galvanic/default.asp (1818 words)

	Emerging Construction Technologies (Site not responding. Last check: 2007-10-23)
		The palm-sized anode consists of a galvanic zinc core surrounded by an active cementitious matrix.
		These anodes are designed to reduce the ring anode corrosion commonly associated with concrete patch repairs and delay the onset of future corrosion.
		Ring anode corrosion is caused by differences in corrosion potential between areas which have been patched and the remaining portions of the structure.
	www.new-technologies.org /ECT/Civil/galvanic.htm (539 words)

	CP BY GALVANIC ANODES. - Corrosionsource Discussion Boards
		Your case is very interesting to analyze the coating conditions, chemical analysis of water and any sample of recovered anodes (if any), and of course operating conditions of the vessel.
		the design was 100 m.amp/sq.m, the welded anodes weight was 60 kg(17 anodes/3.5 kg net), welded in the water level(water level area 25 sq.m).
		the electrochemical efficiency of Al-base anode materials is drastically lower than the 2500 assumed by yourselves for T in degr.
	www.corrosionsource.com /discuss2/ubb/Forum1/HTML/000413.html (349 words)

	NVIC 7-95
		At the anodes, the free electrons are absorbed in a reaction that consumes the oxygen which is dissolved in the surrounding water or in the water absorbed by the surrounding wood.
		Galvanized steel (steel coated with zinc) is an example of an intentional galvanic cell - the zinc acts as a sacrificial anode for the steel in the case of a small penetration of the coating.
		In the galvanic cell, the metal is connected to another, more positive, metal, which draws electrons from it and causes the anode reaction rate of the negative metal to increase to supply those extra electrons.
	www.uscg.mil /hq/g-m/nvic/7_95/n7-95.htm (17408 words)

	Expert: Corrosion and Metallurgical Failure Analysis Expert
		The anodes didn't corrode, which meant that the hulls of the vessels they were supposed to protect did corrode.
		Expert notes that galvanic protection can be either cathodic protection--the use of "galvanic" or "sacrificial" anodes to protect a structure--or it can be the use of an anodic coating (aluminum, zinc, cadmium, or tin) to protect an underlying substrate metal.
		Expert notes that sacrificial protection is usually a form of cathodic protection involving the use of galvanic anodes made of magnesium, zinc, or aluminum alloys to control, usually, corrosion on carbon steel or similar alloys.
	www.intota.com /viewbio.asp?bioID=765779&perID=722268 (5450 words)

	Offshore Technology - Laiken - Corrosion Control Products and Equipment (Site not responding. Last check: 2007-10-23)
		Laiken manufactures both galvanic and impressed current anodes for cathodic protection and offers a wide range of corrosion control equipment which includes field survey equipment for detecting coating failures and protection levels (DCVG and CIPS); holiday detectors, anticorrosive equipment and CP instrumentation.
		For use in soils, zinc anodes are provided with different types of cable according to the environment, and packed with the right amount and composition of backfill needed in order to assure the best performance of the anode.
		Graphite anodes are provided with different types of cable with two possible connection alternatives: center-connected or end-connected; and are also impregnated to assure a longer life to the anode.
	www.offshore-technology.com /contractors/corrosion/laiken (622 words)

	A Study of Electrochemical Efficiencies of Aluminium Galvanic Anodes in Sea Water - Storming Media
		The difference in performance between these anodes in the field trial, and the dichotomy between the results of the field trial and the laboratory test, is partially attributed to the A2 anodes being susceptible to intergranular corrosion.
		This susceptibility is discussed in relation to the behavior of the anode in marine environments.
		The apparent lack of susceptibility to intergranular attack of these A2 anodes in the standard laboratory test and a resultant high anode galvanic efficiency does not indicate, per se, reliable long-term serviceability.
	www.stormingmedia.us /35/3594/A359472.html (291 words)

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