Aluminum coating technology for titanium alloy fasteners

Titanium alloy fasteners are widely used in modern advanced aircraft body structures due to their light weight, high specific strength, fatigue resistance, corrosion resistance and other excellent comprehensive properties. In the aircraft connection assembly, titanium alloy fasteners and aluminum alloy materials There is a high potential difference. If the connection part is not handled properly, it is easy to produce potential corrosion, and serious corrosion will cause the structure to fail and destroy. Therefore, to solve the problem of potential corrosion when the titanium alloy fastener is connected to the aluminum alloy structure, it is It is an important task to ensure the long-life and high-reliability connection of modern aircraft. For the aluminum alloy structure assembling titanium alloy fasteners, there are many methods to prevent potential corrosion. The best solution is to coat the surface of the titanium alloy fasteners. A layer of anti-corrosion aluminum coating. At present, this method has been widely adopted by the aviation industry all over the world. This article focuses on the protection mechanism of titanium alloy fasteners and aluminum alloy structures, the aluminum coating technology of titanium alloy fasteners, and the effect of aluminum coating. Elaboration, to provide efficient and reliable aluminum coating technology for domestic titanium alloy fasteners used in aluminum alloy structures.

Aluminum coating protection mechanism and effect When titanium alloy is assembled on aluminum alloy structure, due to the high potential difference, electrochemical corrosion will occur under the action of electrolyte. There are two basic ways for electrochemical corrosion protection:

(1) Insulate the anode or cathode;

(2) Eliminate the ionic conductivity in the anode or cathode area. Based on the above two approaches, there are mainly the following 4 protection methods:

(1) Fasteners with cadmium or aluminum plating;

(2) Fasteners coated with organic or inorganic coatings;

(3) Use wet primer or elastic sealant during installation;

(4) Zinc-chromium coatings are used to coat fasteners or structural elements. However, none of the above methods can fully protect the surface, and the surface layer produced by some of these methods does not have sufficient toughness or viscosity, and there are High manufacturing costs and other issues, these factors have prompted continuous research to obtain better methods, such as coating a layer of aluminum, fluorine and chromate or molybdenum disulfide on the outer surface of fasteners or structures. Fluorine-containing and chromate-containing coatings have led to the birth of aluminum coating technology. The anti-corrosion aluminum coating for titanium alloy fasteners developed by foreign companies can be coated with uniform thickness, smooth, fine and dense, and better protective performance. The layer can not only meet the high-temperature use conditions of 235, but also does not require additional sealing during the assembly process to prevent electrochemical corrosion. At the same time, it has excellent bonding strength with the base material and will not adversely affect the base material. , Aluminum coatings are used to protect the surface of various titanium alloys and high-strength corrosion-resistant steel fasteners. They have excellent corrosion inhibition. They have good resistance to stress embrittlement under high temperature and high stress. They have superior installation lubrication performance and can It resists various hydraulic fluids, fuels, paint washing agents and cleaning agents without deterioration, good heat resistance and good adhesion.