CORROSION PROCESS OF MULTILAYER ALUMINUM-BRAZED SHEET BY EIS AND EN TECHNIQUES

Longjun Guo, Jihui Wang, Wenbin Hu and Dejing Zhou
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Longjun Guo: Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
Jihui Wang: Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
Wenbin Hu: Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
Dejing Zhou: #x2020;Jiangsu Key Laboratory for Clad Materials, Wuxi Yinbang Clad Material Co., Ltd, Wuxi 214145, P. R. China

Surface Review and Letters (SRL), 2019, vol. 26, issue 06, 1-16

Abstract: The microstructures of AA4045/AA3003Mod./AA4045 aluminum-brazed sheet were observed and determined by stereoscopic digital microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS). The corrosion process of the brazed sheet in the exfoliation corrosion (EXCO) solution was investigated by electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques. The results showed that the brazed sheet was composed of the Al-Si eutectic zone, the precipitates-free zone (PFZ), the band of dense precipitates zone (BDP) and the core material. With the immersion time increased, the capacitive time constant in EIS plot changed from one time constant through two unclear time constants to two clear time constants, and then went back to two unclear time constants again. The maximum relative energy in energy distribution plot (EDP) changed from small scales through middle scales to large scales, and then went back to middle scales. The corrosion process could be divided into four stages: the dissolution of the eutectic α-Al in the resolidified clad in the form of pitting corrosion; the corrosion of the primary α-Al grain boundaries in the form of intergranular corrosion (IGC); the corrosion of the BDP zone in the form of exfoliation corrosion; and the corrosion of the core material in the form of IGC.

Keywords: Multilayer aluminum; electrochemical impedance spectroscopy; electrochemical noise; microstructure; corrosion process (search for similar items in EconPapers)
Date: 2019
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DOI: 10.1142/S0218625X18502037

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