[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.
lead brasspipe jointweldingair tightness testneutral potassium soapdezincificationcorrosion
NETL
NSTL
万方数据
