Corrosion behaviour of dual-coated (zinc/expoxy) rebars in pore-simulated solution with and without chloride


Corrosion of carbon steel rebars embedded in concrete is a recurring problem in construction and leads to economic and human losses. Concrete structures are exposed to a contamination through the pores by gases present in the atmosphere and by contaminants dissolved in water. As Brazil presents a large tropical coast area, the corrosion of reinforcement bars is regularly caused by chloride ions. Hence, mitigation techniques are used to extend the service life of concrete structures and a worldwide disseminated practice is the replacement of carbon-steel rebars for alternative reinforcement materials or coated carbon-steel bars. Some alternatives of coated carbon steel reinforcements commonly used are the adoption of galvanized, epoxy coated or duplex coated (zinc + epoxy) bars. Thus, a study was developed with the objective of understanding and clarifying the behaviour of duplex coated bars used as concrete reinforcement. For this purpose, open-circuit-potential and electrochemical-impedance-spectroscopy measurements were performed using duplex coated bars, with and without a 1.5 mm intentional damage exposing the steel substrate, immersed in a simulated pore solution without and with chloride ions for 270 days. The results indicated that zinc at the rim of defect promotes cathodic protection for the exposed steel. However, the protection time cannot be predicted in the adopted test conditions. Therefore, it is necessary to carry out tests that simulate the real conditions for a longer exposure time.

PACHECO, Mayara Stecanella; CARDOSO, Juliana Lopes; PANOSSIAN, Zehbour. Corrosion behaviour of dual-coated (zinc/expoxy) rebars in pore-simulated solution with and without chloride. In: INTERNATIONAL CORROSION CONGRESS, 21., AND THE INTERNATIONAL CORROSION MEETING, 8., 2021, São Paulo. (on-line). Proceedings on-line… 16 p.  

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