2219-T8铝合金搅拌摩擦焊接头在酸性介质中的腐蚀行为
Corrosion of friction stir welded joints of the 2219-T8 Al alloy in acidic solutions

2219铝合金可作为火箭燃料贮箱的主要结构材料，搅拌摩擦焊是其理想的焊接方法之一。目前对2219铝合金搅拌摩擦焊接头在酸性介质中的腐蚀问题鲜有报道。该文采用极化曲线和浸泡腐蚀实验对2219-T8铝合金搅拌摩擦焊接头在0.5 mol/L NaCl溶液（pH 2）中的腐蚀行为进行了研究，并通过光学轮廓仪分析了腐蚀形貌、腐蚀深度和密度。结果表明：与母材相比，热影响区的腐蚀行为出现了分化，远缝区耐蚀性能下降，而近缝区耐蚀性能提高；热机械影响区和焊核区的耐蚀性能提高。由于母材和热影响区远缝区的腐蚀电位更负，对接头其他区域起到了阴极保护作用。与中性介质相比，酸性介质中主要的阴极反应为析氢反应，降低了接头各区的腐蚀电位和点蚀电位。
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.