M. JariyaboonA. J. DavenportR. AmbatB. J. ConnollyS. W. WilliamsD. A. PriceUniversity of BirminghamMahidol UniversityDanmarks Tekniske UniversitetBAE Systems plcCranfield University2018-05-032018-05-032011-01-01Materials Science and Technology. Vol.27, No.1 (2011), 208-21317432847026708362-s2.0-78650953270https://repository.li.mahidol.ac.th/handle/20.500.14594/11910Corrosion behaviour of the banded structure known as 'onion ring' in the nugget of friction stir weld AA2024-T351 was investigated to find the relation to microstructure. A micro-electrochemical cell with a 50 μm diameter glass pipette tip was used for electrochemical measurements. It was found that onion rings consisted of two bands: 'dark' bands that contain fewer constituent particles but show extensive precipitation of S phase and 'light' bands that contain fewer S phase precipitates but greater numbers of constituent particles. Electrochemical results showed that the light band has more noble (less active) open circuit potential compared to the dark band. Microstructurally, this is due to the lower number of S precipitates and therefore the possibility of higher Cu solid solution within the band compared to that of the dark band. © 2011 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute.Mahidol UniversityEngineeringMaterials SciencePhysics and AstronomyArticleSCOPUS10.1179/174328409X425254