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Laboratory evaluation of sacrificial anode materials for cathodic protection of reinforced concrete bridges
Laboratory evaluations were conducted on a series of anode materials that could be used for sacrificial cathodic protection (CP) of reinforced concrete bridge decks. These included Al, Mg and Zn alloys. Anodes were fabricated into test coupons and coupled to small lengths of reinfoceing steel. The anode-steel couples were placed in simulated concrete environments consisting of sealed containers filled with silica sand treated with a mixed alkali solution containing 6 kg.m-3 (10 lbs.yd-3) of chloride ion (Crl(-)) by volume of sand. The treated sands were dried to obtain resistivities of 23 Ohm.m, 100 Ohm.m and 260 Ohm.m. Measurements of current flow, circuit resistance, potential and depolarization were made over 18 weeks. Current flow from anode to steel decreased with an increased resistivity of the environment. For resistivities typical of those encountered in field concretes in atmospherically exposed structuress (>= 100 Ohm.m), current flows < 10 mA.m-2 (1 mA.ft-2) were measured. Greatest current outputs were obtained from Al alloy anodes. Mg anodes performed poorly in resistivities near 100 Ohm.m. Depolarization values measured 4 h after interruption of current exceeded the NACE criterion of 100 mV for most of the anodes tested in all three environments. However, results may have been overly optimistic, as failure of the rebars to exhibit significant corrosion even when not coupled to anodes indicated relatively low corrosion rates despite the large amounts of Cl(-) added to the sand. Driving voltages were greatest for the Al series of anodes, and were smaller for both penny scrap Zn and Mg anodes, indicating the latter two may not offer significant potential to protect steel in high-resistivity environments. Loss of anode material may be greater under conditions of self-corrosion than when galvanically coupled to steel. This was especially true for the Al alloy anodes. If these prove to be viable field anodes, multiple grounds to rebar mats must be made to avoid rapid consumption of anodes if connection to steel is lost during service.
Laboratory evaluation of sacrificial anode materials for cathodic protection of reinforced concrete bridges
Laboratory evaluations were conducted on a series of anode materials that could be used for sacrificial cathodic protection (CP) of reinforced concrete bridge decks. These included Al, Mg and Zn alloys. Anodes were fabricated into test coupons and coupled to small lengths of reinfoceing steel. The anode-steel couples were placed in simulated concrete environments consisting of sealed containers filled with silica sand treated with a mixed alkali solution containing 6 kg.m-3 (10 lbs.yd-3) of chloride ion (Crl(-)) by volume of sand. The treated sands were dried to obtain resistivities of 23 Ohm.m, 100 Ohm.m and 260 Ohm.m. Measurements of current flow, circuit resistance, potential and depolarization were made over 18 weeks. Current flow from anode to steel decreased with an increased resistivity of the environment. For resistivities typical of those encountered in field concretes in atmospherically exposed structuress (>= 100 Ohm.m), current flows < 10 mA.m-2 (1 mA.ft-2) were measured. Greatest current outputs were obtained from Al alloy anodes. Mg anodes performed poorly in resistivities near 100 Ohm.m. Depolarization values measured 4 h after interruption of current exceeded the NACE criterion of 100 mV for most of the anodes tested in all three environments. However, results may have been overly optimistic, as failure of the rebars to exhibit significant corrosion even when not coupled to anodes indicated relatively low corrosion rates despite the large amounts of Cl(-) added to the sand. Driving voltages were greatest for the Al series of anodes, and were smaller for both penny scrap Zn and Mg anodes, indicating the latter two may not offer significant potential to protect steel in high-resistivity environments. Loss of anode material may be greater under conditions of self-corrosion than when galvanically coupled to steel. This was especially true for the Al alloy anodes. If these prove to be viable field anodes, multiple grounds to rebar mats must be made to avoid rapid consumption of anodes if connection to steel is lost during service.
Laboratory evaluation of sacrificial anode materials for cathodic protection of reinforced concrete bridges
Laboratoriumsuntersuchung von Opferanodewerkstoffen für den kathodischen Schutz von Stahlbetonbrücken
Whiting, D.A. (author) / Nagi, M.A. (author) / Broomfield, J.P. (author)
Corrosion, Houston ; 52 ; 472-479
1996
8 Seiten, 7 Bilder, 6 Tabellen, 18 Quellen
Article (Journal)
English
kathodischer Korrosionsschutz , Laboratoriumsversuch , Opferanode , Stahlbeton , Brücke (Bauwerk) , Zinklegierung , Zink , Magnesiumlegierung , Aluminiumzinklegierung , Aluminiummagnesiumlegierung , Ohm-Widerstand , Kaliumverbindung , Basen , Natronlauge , Chlorid , praktische Untersuchung , elektrisches Potenzial , Gewichtsverminderung , Bewertungsmethode , elektrochemische Polarisation , unlegierter Stahl , Armierung
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