Anticorrosive Improving On Typical Tube Inner Structure Of Aircraft

The corrosion of tube inner structure is a serious problem which influence flight security and economically repair. A series of key technology questions were researched in this paper systematically, which include the main reason and mechanism for the corrosion occurrence in the tube inner structure on typical plane, accelerated corrosion test methods, anticorrosive technology improving, improvement of spraying technology, the development of nozzle on the spraying equipment, the optimization of spraying parameter, and the evaluation method of coating after improvement of anticorrosion, etc. Several innovations were made in this paper as following.1) The reasons for the corrosion of typical tube inner structure on service aircraft were revealed. The main reason for the corrosion occurrence in the major axles of the tail horizontal wing on certain plane could be ascribed to three aspects. First, there are gaps at the junction of the major axles of the tail horizontal wing, where the corrosive medium could permeate and difficult to be discharged, and the local environment was abominable. Second, the anticorrosive technical measure is unfit for the inner surface, and the anticorrosive performance of coating is bad. Third, the material 30CrMnSiNi2A high-strength steel is sensitive to the corrosive environment, and welding will increase the sensitivity of material, accelerate the initiation and development of corrosion.2) The corrosion mechanism of typical tube inner structure on service aircraft was discovered. The characteristic of stress corrosion damage of metal substrate near the welding seam was found in this paper. With the co action of corrosive environment and residual stress, stress corrosion damage will generate and develop constantly around the welding seam, fatigue crack will generate by the influence of cyclic load on the location where the stress corrosion damage is serious, even result in rupturing.3) Replaced available coating TB06-9 which painted on the inner surface of the major axles with heavy-duty coating SLF(as priming paint) and nano-composite coating IMR(as surface paint), and realized the improvement of anticorrosive coating system of tube inner structure on typical aircraft.4) The method of automatic no-air painting for tube inner structure was put forward. Analyze in terms of antiseptic mechanism, the corrosive environment of wetting and drying alternately in tube will increase the internal stress of coating, which will reduce the cohesion of coating and base, influence the shielding function of coating to the hydrone and other ions directly. And spray painting can improve the uniformity and combine intensity with the base of coating obviously, thus improve the anticorrosive performance of the coating.5) By analyzing and disassembling many kinds of nozzles of domestic and international, designed and trial-produced repeatedly on the basis of getting the operation principle. Succeed in developing special nozzle with good performance. By optimizing the processing parameter of spraying pressure, rotational speed of work piece, viscosity of coat, solidification temperature, solidification time, etc, solved the technological problem in development of automatic no-air painting equipment for tube inner structure.6) The accelerated corrosive environmental spectrum and the accelerated corrosion test methods were put forward for the local environment and characteristic of corroding of tube inner structure on typical plane. The corrosion features the typical aircraft structures appeared during the active service were reappeared well under the condition of the laboratory, and have offered test methods for the studying of corrosion process of tube inner structure and evaluating anticorrosive quality and service life of the coating system. 7) Anticorrosive quality of coating after the improvement of anticorrosion was evaluated by the accelerated corrosion test method that was presented in this paper. The result indicated that the life period of traditional TB06-9 coating will increase 12times by improving the painting method only. And the life period of spray coating will be increased over 50times if replaced TB06-9 coating by heavy-duty coating SLF or heavy-duty coating SLF+ nano-composite coating IMR.8) The improved anticorrosive technical measures in this paper was already succeed in popularizing and apply to major axles of the tail horizontal wing on certain serial plane. The endoscope result showed that the coating painted on the whole tube inner face was improved obviously after the anticorrosive improving.