飞机生保系统氧气导管接头腐蚀原因分析

Analysis of corrosion causes for oxygen pipe joints in aircraft life support system

[目的]飞机生保系统氧气导管接头装机后多次发生腐蚀问题,为保证飞机质量安全,亟需明确其腐蚀原因。[方法]针对小平管嘴与外套螺母配合面及附近区域均出现腐蚀的现象进行了形貌、组织及成分分析,并通过模拟实验来验证腐蚀成因。[结果]确定了表面腐蚀产物为不规则及泥纹花样的Cu、Zn氧化物,且存在较高含量的K、Ca、Na异常元素。氧气导管小平管嘴沟槽处容易残留中性钾皂液,在表面浸润的情况下形成了大片不规则的钾皂残留物;其余开放表面接触过中性钾皂后,在未洗净的情况下易产生不规则及泥纹花样的Cu、Zn氧化物颗粒。另外,由于焊接后小平管嘴表层脱锌形成了疏松多孔组织,因此其表面更容易吸附钾皂成分,从而加速腐蚀。[结论]氧气导管在气密试验后表面残留中性钾皂成分是导致其腐蚀的根本原因。建议气密试验后将导管彻底洗净或更换气密试验检测剂。

[Introduction]Corrosion has occurred many times after the installation of oxygen pipe joints in the aircraft life support system,and it is urgent to clarify the corrosion causes to ensure the quality and safety of the aircraft.[Method]Corrosion was found on the mating surface between the flat nozzle and outer nut and the adjacent area.The morphology,microstructure,and composition were analyzed for the corroded and uncorroded areas.A simulation comparison experiment was carried out to verify the causes of corrosion on the flat nozzle surface for the installation of oxygen pipe.[Result]It was determined that the corrosion products were Cu and Zn oxides with irregular and muddy patterns,and there existed abnormally high contents of K,Ca,and Na elements.The neutral potassium soap solution is easy to remain in the groove of the flat nozzle,resulting in the formation of large irregular soap residues on the surface.Cu and Zn oxide particles with irregular and muddy patterns can be easily formed on the remaining open surfaces which are not washed thoroughly after contact with neutral potassium soap.Due to the surface of the flat nozzle is dezincified to form a loose and porous structure after welding,the surface is easier to adsorb the potassium soap component than usual,which accelerates the surface corrosion process.[Conclusion]The residue of the constituent of neutral potassium soap on the surfaces of oxygen pipe joints during the air tightness test is the most important cause for the corrosion.It is recommended that the pipe joints should be washed thoroughly after air tightness test or the neutral potassium soap solution used as the indicator in the air tightness test should be replaced.