Study of the galvanic potential of zinc and steel to elucidate galvanized steel and dual-coated (zinc/epoxy) rebar potentials in concrete structures

Abstract:

The monitoring of the open circuit potential of the reinforcement is used to identify regions in concrete structures with active processes of corrosion. For carbon steel rebars, ASTM* C876 (2015) standard provides the correlation between the numerical value of the potentials measured and the steel rebar condition, defining a range with a greater than 90 % probability of occurrence of corrosion, or a greater than 90 % probability of not being corroded and, between these, an uncertain corrosion condition. However, the potential values established for carbon steel rebars are not applicable for galvanized steel rebars because the zinc and the steel form a galvanic couple and the value of the open circuit potential is a function of the exposed area ratio of the zinc and the steel. In order to verify and suggest a classification similar to that of the carbon steel rebars for galvanized steel rebars, the open circuit potential of the galvanic couple of zinc/steel was measured considering various area ratios, in simulated pore solutions with and without chloride ion contamination. The obtained potential values were compared to the potential of galvanized and dual-coated (zinc/epoxy) rebars, embedded in concrete.


Reference:
CARDOSO, Juliana Lopes; ALVES, Rafael Ribeiro Urano; PACHECO, Mayara Stecanella; PANOSSIAN, Zehbour. Study of the galvanic potential of zinc and steel to elucidate galvanized steel and dual-coated (zinc/epoxy) rebar potentials in concrete structures. In: NACE INTERNATIONAL CORROSION CONFERENCE, 2019, Nashville, Tennessee/EUA. Proceedings… 15 p.

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