Understanding the galvanic interactions between AA2024T3 and mild steel using the scanning vibrating electrode technique Uyime Donatus * , George E. Thompson, Hong Liu, Xiaorong Zhou, Zuojia Liu Corrosion and Protection Centre, School of Materials, The University of Manchester, Manchester M13 9PL, UK highlights  Use of SVET in monitoring the galvanic interactions between AA2024T3 and mild steel under near-ambient temperature conditions.  AA2024T3 is anodic to mild steel within the solution temperature range of 21e35  C.  Polarity reversal of the couple starts to occur from 45  C and above. article info Article history: Received 22 November 2014 Received in revised form 10 April 2015 Accepted 16 May 2015 Available online 21 May 2015 Keywords: Alloys Electrochemical techniques Corrosion abstract The scanning vibrating electrode technique has been used to characterize the galvanic interactions be- tween AA2024T3 and mild steel at room temperature and elevated solution temperatures up to 60  C in naturally aerated 3.5% NaCl solution. The work shows that from a solution temperature of 43  C and above, highly localised anodic activities with high intensities occur on the mild steel, compared with the anodic activities occurring on the AA2024T3 alloy in a couple system of the two alloys. The highly localised activities on the mild steel were not observed at 34±1  C with the surface showing no distinct corrosion activities and AA2024T3 alloy was completely the bulk anodic material at this solution tem- perature. At room temperature, AA2024T3 was also the bulk anode, although mild anodic activities were detected on the surface of the mild steel alloy. The local corrosion activities revealed by the scanning vibrating electrode technique were in agreement with the micrographs of the surfaces of the alloys after the immersion tests. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Understanding the influence of environmental temperature on the corrosion behaviour of transportation components is very crucial to the design of aerospace and automotive vehicles. It will be interesting to learn that just a little variation in the solution tem- perature of a coupled AA2024T3 aerospace alloy and mild steel may significantly affect the corrosion kinetics. In this work, scanning vibrating electrode technique (SVET), galvanic polarization technique, and optical microscopy have been employed to investigate the in-situ galvanic interaction between AA2024T3 and mild steel with varying solution temperatures. It is revealed that, highly localised events play a major role in the galvanic interaction between AA2024T3 and mild steel, particularly at elevated solution temperatures. The scanning vibrating electrode technique (SVET) has proved to be a novel tool for investigating local cathodic activity and anodic activity. The SVET is gaining increased relevance recently, with much work having been done by Battocchi, Simoes and co workers on Al alloys, Mg-rich coatings on Al alloys and ironezinc cell [1e3]. More recently, Williams and co-workers have used it extensively on Mg alloys [4,5]. This technique works by recording potential gra- dients perpendicular to the ionic current flux lines between suc- cessive cathodic and anodic regions along the path of the probe tip as it traverses the specimen while vibrating at a constant ampli- tude. A distance of tens of microns is required for the probe to be able to record potentials resulting from the electrolyte resistance to current flow and as such, the SVET underestimates corrosion ac- tivities occurring below the set probe height [5]. This knowledge is used in analysing the results in this work and the analyses are based on the intensities of the anodic activities occurring on the surface of the coupled alloys. The results were compared with galvanic measurements obtained from a multichannel potentiostat. * Corresponding author. E-mail address: uyime.donatus@postgrad.manchester.ac.uk (U. Donatus). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys http://dx.doi.org/10.1016/j.matchemphys.2015.05.040 0254-0584/© 2015 Elsevier B.V. All rights reserved. Materials Chemistry and Physics 161 (2015) 228e236