Fastener connection is a common part of the aircraft, is also an important connector of the aircraft, also known as the aircraft's AIDS to navigation. After disassembly and assembly of aircraft fasteners, corrosion products can penetrate into fastener holes, causing corrosion of hole wall and fasteners. The steel fasteners which are often disassembled and disassembled are prone to corrosion. What are the main reasons for the corrosion of steel fasteners? What are the anti-corrosion protection measures for steel fasteners? According to the understanding, Zhonggu standard parts network will share relevant knowledge./p>

1. Analysis of main reasons for corrosion of steel fasteners

Fig. 1 Corrosion of fasteners after disassembly

1) The corrosion resistance of fastener surface treatment layer is poor. After inspection, it was found that the main corrosion was steel fasteners with a diameter of 8 mm or less. The surface treatment of bolts and gaskets of this part of fasteners is mainly carried out by galvanizing in China. The zinc coating is not only poor in corrosion resistance in marine environment, but also easy to fall off after disassembly and assembly.

2) The fastener hole wall is not protected. In aircraft manufacturing, if there is no special surface protection for fastener hole wall, the corrosion of matrix will be directly caused by the immersion of corrosive medium.

3) The surface paint layer failed. After the fastening connection structure is disassembled, the coating at the fastener hole and joint surface breaks. If effective supplementary protective measures are not taken during re installation, the corrosion medium can directly penetrate into the fastener hole and joint surface, resulting in corrosion of the fastener and hole wall, and extending from the fastener hole to the body structure.

Therefore, the corrosion protection of the connection area of steel fasteners which are often disassembled should be carried out from the improvement of fastener surface treatment, fastener hole wall protection and improvement of assembly process.

2. Corrosion protection measures for steel fasteners

According to the analysis of corrosion causes of steel fasteners which are often disassembled and disassembled, and referring to the experience of Aircraft Corrosion protection design and repair at home and abroad, the corrosion protection measures are formulated.

1) Improve the surface treatment process of fasteners. According to the test results, the corrosion resistance of cadmium plating in marine environment is obviously better than that of zinc plating process. Therefore, the washer and bolt which used the galvanizing passivation process were changed to cadmium plating passivation process for surface treatment.

2) Surface protection of fastener hole wall. For the hole wall of aluminum alloy structural fastener without surface treatment, alodine is used for surface treatment, and then a layer of anti-corrosion primer is applied; for the hole wall of steel structure fastener without surface treatment, a layer of phosphating primer is applied.

3) Wet assembly of fasteners. After the primer of fastener hole wall is cured, the fastener is wet assembled with grease. The use of grease assembly can not only play a sealing role to prevent the medium from penetrating into the gap, but also facilitate the disassembly of fasteners and the field construction.

4) Spray corrosion inhibitor. After the fastener is assembled, a layer of soft film water displacement corrosion inhibitor is sprayed on the surface of fastening connection area. Corrosion inhibitor is an important means of corrosion prevention and control. It has good permeability and water displacement. It can quickly penetrate into the crack of aircraft structure, and replace the water in the gap and metal surface to the outside, so as to isolate the metal from water. At the same time, a protective film is deposited on the metal surface to effectively delay the corrosion of metal materials.

結論:

1) By taking comprehensive protection measures on surface protection and assembly sealing, the corrosion problem of steel fastening connection area which is often disassembled and disassembled can be effectively solved, which can be widely applied in aircraft manufacturing, use and maintenance.

2) The protective measures such as painting the fastener hole wall and spraying corrosion inhibitor after assembly can be used for reference in corrosion protection design and repair of other connecting structures.