D.Mendeleev University of Chemical Technology of Russia, Moscow, Russia:

M. D. Solonin, Postgraduate Student at the Department of Innovative Materials and Corrosion Protection, e-mail: soloninmixa@gmail.com
N. A. Asnis, Lead Engineer at the Department of Innovative Materials and Corrosion Protection, Candidate of Technical Sciences, e-mail: asnis@mail.ru
N. S. Grigoryan, Professor at the Department of Innovative Materials and Corrosion Protection, Associate Professor, Candidate of Chemical Sciences, e-mail: ngrig108@mail.ru
T. A. Vagramyan, Head of the Department of Innovative Materials and Corrosion Protection, Professor, Doctor of Technical Sciences, e-mail: vagramyan@muctr.ru

This paper examines some issues related to the gold plating of fine tungsten wires. The key properties of tungsten are described that determined the choice of that material for manufacturing reflector curtains. Available information sources are considered which recommend cleaning of tungsten wires before electroplating. The paper gives a brief overview of electrolytes used in gold electroplating, as well as achievable gold plating rates. The authors offer a review of literature on existing electrochemical treatment machines for fine metal wires. It is shown that the high-rate cleaning (which only takes a few seconds) of tungsten wire can be more efficient when using alternating or reverse current. Thus, the best performance was achieved when a 50 Hz current was applied at the solution temperature of 60 ^oC (the solution contained 180 g/l NaOH) and the average current density of 180 A/dm² for 3–4 sec. A similar cleaning performance was achieved when the same alkaline solution and the same solution temperature were used, but when reverse current was applied at the average density of 20 A/dm² for 5 sec, with cathodic and anodic pulses having different lengths: 0.2 sec for the anodic one and 0.8 sec for the cathodic one. It was found that the above conditions for pre-treatment and alkaline cleaning of fine tungsten wires are associated with minimal alteration of the mechanical properties of such wires caused by hydrogen pick-up.

1. Nadiradze A. B., Shaposhnikov V. V., Smirnov V. A., Maksimov I. A., Kochura S. G. et al. Understanding the erosive effect of stationary plasma engine jets on the reflector curtains of large spacecraft antennas. Siberian Aerospace Journal. 2008. No. 4. pp. 120–124.
2. Denisova E. I., Kartashov V. V., Rychkov V. N. Applied materials science: Metals and Alloys : Learner’s guide. Yekaterinburg : Izdatelstvo Uralskogo universiteta, 2018. 216 p.
3. Denisov V. P. Production of electrical sources of light. Moscow : Energiya, 1975. 488 p.
4. Yampolskiy A. M. Electrochemical deposition of noble and rare metals. 4^th revised edition. Leningrad : Mashinostroenie (Leningrad branch), 1977. 96 p.
5. Gorelov V. P., Gorelov S. V., Gorelov V. S., Grigoriev E. A. Electrical engineering materials. Ed. by V. P. Gorelov. 5th edition. Moscow; Berlin : Direkt-Media, 2016. 340 p.
6. Azhogin F. F., Belenkiy M. A., Gall I. E. Electroplating : Handbook. Moscow : Metallurgiya, 1987. 736 p.
7. GOST 19671–91. Tungsten wire for light sources. Specifications. Introduced: 01.01.1993.
8. Bauer T. Effective deposition of metal coatings on copper wire. New Technologies and Equipment. 2008. No. 1. pp. 7, 8.
9. Berson V. S., Chayko V. Yu. Wire electroplating lines. Nauka i tekhnika. 2005. No. 6. pp. 21–25.
10. Ehrhardt R. A., Humphrey R. G. Method of making contact wires. Patent 2429222 A US. Applied: 5.06.1943. Published: 21.10.1947.
11. Levit M. L., Sorokina E. V., Brodetskiy I. I., Askinazi V. E. Wire electroplating unit. Patent RF, No. 2064022. Applied: 10.12.1991. Published: 20.07.1996.
12. Pavlyutenkova V. Sh., Kamalutdinov M. K., Grigoriev V. V., Shakirova R. G. Device for electroplating of wire. Patent USSR, 1650787A1. Applied: 29.07.1988. Published: 23.05.1991.
13. Andreev A. V., Katkov A. E. Device for application of coating to wire by electrolysis. Patent RF, No. 2185464. Applied: 26.06.2000. Published: 20.07.2002.
14. Zheng Taikui, Deng Jun, Ma Longke. Continuous electroplating production line of ultrafine metal wire. Patent 110004474 CN. Applied: 22.05.2019. Published: 12.07.2019.
15. Bo Xinwei, Liu Qi, Wang Xiaoyu, Yang Hao et al. Gold plating device for refractory metal wire. Patent 204417623U CN. Applied: 11.12.2014. Published: 24.06.2015.
16. Lushpinin K. V., Levandovskiy V. P., Koryagin A. V., Sychev A. I. et al. Method for applying galvanic coating on precision metal threads and installation for its implementation. Patent RF, No. 2751355. Applied: 26.02.2021.
Published: 13.07.2021.
17. Bo Xinwei, Liu Qi, Wang Xiaoyu, Yang Hao et al. Processing process for plating gold on insoluble metal wire. Patent 104451804B CN. Applied: 11.12.2014. Published: 25.01.2017.
18. Qian Su, Quansheng Liu, Shuliang Liang, Chengfeng Luo et al. Equipment and method for plating gold or plating palladium on surface of metal wire. Patent 102586830A CN. Applied: 10.01.2011. Published: 18.07.2012.
19. Burkat G. K. Electrodeposition of precious metals. 6^th edition: Iss. 1. St Petersburg : Politekhnika, Bibliotechka galvanotekhnika, 2009. 188 p.