Conducting corrosion resistant nickel coating for contacts of the system of aircraft underwater locator beacons

The paper deals with the development of manufacturing methods of improving the functionality and reliability of the electric contact made of titanic VT3-1 alloy. This alloy is used in the development of electrical contacts for acoustic beacons used on airplanes of various airline companies. Solving the problem of increasing the life of acoustic beacons (up to 90 days) is directly related to an increase in the stability of the electrochemical characteristics of the contact. To ensure the stable behavior of the electric potential (not more than 0.5 V) at the contact, a method of gas-dynamic spraying of a protective coating based on nickel of increased thickness is proposed. Single-layer and two-layer coatings obtained from different grades of powder mixtures were tested. The regularities of the process of electrochemical breakdown and passivation of protective coatings during comparative short-term tests were studied. Based on the test results, a single-layer gas-dynamic coating of the composition (Ni + Al₂O₃) formed from the powder mixture of grade N3-00-02 was chosen. The microstructure, phase composition, microhardness, porosity and adhesive strength of Ni-based protective coating were investigated. Electrochemical tests of electrical contact with the investigated coating in the sea water environment depending on the time factor were carried out. Increased thickness of the coatings combined with low open porosity and high adhesive strength provided stable behavior of the electric potential in the process of applying it to the working surface of the titanium alloy contacts VT3-1. This ensures reliable electrochemical protection of contacts in the sea water environment for 90 days.