Corrosion of friction stir welded joints of the 2219-T8 Al alloy in acidic solutions
KANG Ju1,2, LIANG Suying3, WU Aiping1, WANG Guoqing4
1. State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;
2. State Grid Jibei Electric Power Co. Ltd. Research Institute, North China Electric Power Research Institute Co., Ltd., Beijing 100045, China;
3. Shougang Institute of Technology, Beijing 100144, China;
4. China Academy of Launch Vehicle Technology, Beijing 100076, China
Abstract：Al alloy (AA) 2219 has potential for use in liquid cryogenic rocket fuel tanks, with friction stir welding (FSW) as a suitable welding method. However, there is limited data on the corrosion of FSW AA2219-T8 joints in acidic solutions. Therefore, the corrosion of an FSW AA2219-T8 joint in an acidic chloride solution (pH 2, 0.5 mol/L NaCl) was characterized using potentiodynamic polarization and corrosion immersion tests. An optical profilometer was used to analyze the corrosion morphology, depth and density of the corroded cross-section surface and identify the corrosion mechanism. The results show that the corrosion resistance differs throughout the whole heat-affected zone (HAZ) with the worst corrosion region far from the welding seam. The corrosion resistance significantly increases in the thermomechanically affected zone (TMAZ) and the weld nugget zone (WNZ). The WNZ, TMAZ and near seam regions of HAZ are less affected because they are cathodes to other regions and are protected from corrosion. Unlike in neutral solutions, the primary reduction reaction is hydrogen evolution, which reduces the corrosion potential and pitting potential in each region.
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2017, Vol. 57 
