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

A. A. Abrashov, Cand. Eng., Associate Prof., Dept. of Innovative Materials and Corrosion Protection, e-mail: abrashov.a.a@muctr.ru
Ya. V. Tolmachev, Postgraduate Student of the Dept. of Innovative Materials and Corrosion Protection, e-mail: vetolmyan@gmail.com
N. S. Grigoryan, Cand. Chem., Associate Prof., Prof., Dept. of Innovative Materials and Corrosion Protection, e-mail: grigorian.n.s@muctr.ru
T. A. Chudnova, Cand. Eng., Associate Prof., Dept. of Innovative Materials and Corrosion Protection, e-mail: violatan@yandex.ru

A technology for the deposition of black nickel-based coatings with high protective ability, adhesion strength and wear resistance for 50A and 50RA, 09G2S, Steel 20, Steel 30, 08X17 steel grades has been developed. Sulfate nickel plating electrolyte with the following parameters was chosen as the base solution, g/L: 100 – NiSO₄·7H₂O; 40 – ZnSO_4·7H₂O; 25 – H₃BO₃; 15 – (NH₄)₂SO₄; 7 – NaH₂PO₂; pH = 4.5–5.5, temperature 50–55 °C. It has been experimentally established that good quality coatings are deposited from the solution with sodium hypophosphite concentration of 5–10 g/L. A two-stage current mode has been selected that makes the formation of black coatings possible: stage I – during the first 10 minutes of the process, the current density gradually rises from i₁ = 0.02 A/dm² to i₂ = 0.2 A/dm², stage II – a sharp increase in current density up to i₃ = 1.5 A/dm², with the electrolysis continuing for another 10 minutes. It was shown that the average thickness of the coating deposited from the solution at a constant current density is 6 μm, whereas coatings with a thickness of 10 μm are formed during the stepwise deposition. Wherein, the electrolyte in the first case has a positive leveling, while in the second case the leveling is negative. It was determined that the coating consists of nickel oxides NiO, Ni₂O₃, zinc oxide ZnO, nickel phosphide Ni₂P, as well as nickel hydroxide Ni(OH)₂ and zinc hydroxide Zn(OH)₂. It was determined that the black nickel-based coatings obtained are not only not inferior, but are superior to black chromium coatings in terms of wear resistance and protective ability.
The researches were carried out using D. Mendeleev Center for collective use of scientific equipment, within the framework of the project No. 075-15-2021-688.

1. Takadoum J. Black coatings: a review. The European physical journal applied physics. 2010. Vol. 52. 30401.
2. Azli N. N. A., Amin N. M., Oluhende S. T., Mohamad S. N. A., Fadil N. A. Electroless deposited black nickel-phosphorous solar absorber coatings on carbon steel: effect of plating bath pH. Mater. Today. 2021. Vol. 39. pp. 1071–1076.
3. Meshalkin V. P., Abrashov А. А., Vagramyan Т. А., Grigoryan N. S., Utochkina D. S. Development and study of properties of a new protective and decorative, conversion, environmentally friendly, molybdenum-containing coating of galvanized surfaces. Doklady Akademii nauk. 2018. Vol. 480. No. 5. pp. 555–558.
4. Evangelisti L., Vollaro R. D. L., Asdrubali F. Latest advances on solar thermal collectors: a comprehensive review. Renew. Sustain. Energy Rev. 2019. Vol. 114. 109318.
5. Rudenko M. F., Kravtsov Е. Е., Idiatulin S. А. Effective surfaces of solar receivers. Khimicheskoe i neftegazovoe mashinostroenie. 1998. No. 7. pp. 33–35.
6. Aleshina V. Kh., Abrashov А. А., Grigoryan N. S., Vagramyan T. A. Low-temperature deposition process for black phosphate-selenide coatings. CIS Iron and Steel Review. 2021. Vol. 22. pp. 92–95.
7. Gogna P. K., Chopra K. L. Structure-dependent thermal and optical properties of black nickel coatings. Thin Solid Film. 1979. Vol. 57. pp. 299–302.
8. Lee T. K., Kim D. H., Auh P. C. The optical characteristics of black chrome solar selective films coated by the pulse current electrolysis method. Solar Energy Materials and Solar Cells. 1993. Vol. 29. pp. 149–161.
9. Mennucci M. M., Montes R., Bastos A. C., Monteiro A. et al. Nanostructured black nickel coating as replacement for black Cr(VI) finish. Appl. Sci. 2021. Vol. 11. 3924. DOI: 10.3390/app11093924
10. Estrella-Gutiérrez M. A., Lizama-Tzec F. I., Arés-Muzio O., Oskam G. Influence of a metallic nickel interlayer on the performance of solar absorber coatings based on black nickel electrodeposited onto copper. Electrochimica Acta. 2016. Vol. 213. pp. 460–468.
11. Somasundaram S., Pillai A. M., Rajendra A., Sharma A. K. High emittance black nickel coating on copper substrate for space applications. Journal of Alloys and Compounds. 2015. Vol. 643. pp. 263–269.
12. Hadi S., Buwono H. P., Setiawan A., Valeria S. S. M., Setyawan H. Testing of black chromium coating on low carbon steel. IOP Conf. Series: Materials Science and Engineering. 2021. Vol. 1073. 012075. DOI: 10.1088/1757-899X/1073/1/012075
13. Jeeva P. A., Karthikeyan S., Narayanan S. Performance characteristics of corrosion resistant black coatings. Procedia Engineering. 2013. Vol. 64. pp. 491–496.
14. Abrashov A. A., Grigoryan N. S., Vagramyan T. A., Shcherbina E. A. Durable light-absorbing coatings for structural steels. CIS Iron and Steel Review. 2020. Vol. 19. pp. 71–74.
15. Kotsedi L., Nuru Z. Y., Mthunzi P., Muller T. F. G. et al. Femtosecond laser surface structuring and oxidation of chromium thin coatings: black chromium. Appl. Surf. Sci. 2014. Vol. 321. pp. 560–565.
16. Nunes R. A. X., Costa V. C., Sade W., Araújo F. R., Silva G. M. Selective surfaces of black chromium for use in solar absorbers. Materials Research. 2018. Vol. 21, Iss. 1. e20170556.
17. Medeiros I. D. M., Gomes K. C. Selective solar surface solar based on black chromium: Influence of electrodeposition parameters in the absorption of surfaces. Materials Research. 2019. Vol. 22, Iss. 2. e20180625.
18. Wilbur S., Abadin H., Fay M., Yu D. et al. Toxicological profile for chromium. Agency for Toxic Substances and Disease Registry (US). Atlanta, GA, USA, 2012. 592 p.
19. World Health Organization. Chapter 6.4–Chromium. In Air Quality Guidelines for Europe, 2^nd ed.; European Series No. 91; WHO Regional Publications: Copenhagen, Denmark, 2001. pp. 1–14.
20. Kimbrough D. E., Cohen Y., Winer A. M., Creelman L., Mabuni C. A critical assessment of chromium in the environment. Crit. Rev. Environ. Sci. Technol. 1999. Vol. 29. pp. 1–46.
21. Gharbi O., Thomas S., Smith C., Birbilis N. Chromate replacement: What does the future hold? Materials Degradation. 2018. Vol. 2, Iss. 12. pp. 1–8. DOI: 10.1038/s41529-018-0034-5
22. Pellerin C., Booker S. M. Reflections on hexavalent chromium: health hazards of an industrial heavyweight. Environmental Health Perspectives. 2000. Vol. 108, Iss. 9. pp. A402–A407. DOI: 10.1289/ehp.108-a402
23. Rahman Z., Singh V. P. The relative impact of toxic heavy metals (THMs) (arsenic (As), cadmium (Cd), chromium (Cr)(VI), mercury (Hg), and lead (Pb)) on the total environment: an overview. Environmental Monitoring and Assessment. 2019. Vol. 191, Iss. 7. DOI: 10.1007/s10661-019-7528-7
24. Vaiopoulou E., Gikas P. Regulations for chromium emissions to the aquatic environment in Europe and elsewhere. Chemosphere. 2020. Vol. 254. 126876.
25. Kalidhasan S., Kumar A. S. K., Rajesh V., Rajesh N. The journey traversed in the remediation of hexavalent chromium and the road ahead toward greener alternatives – A perspective. Coord. Chem. Rev. 2016. Vol. 317. pp. 157–166.
26. Smirnov К. N. Some recommendations for monitoring the performance of galvanic solutions. Galvanotekhnika i obrabotka poverkhnosti. 2005. Vol. ХIII, No. 2. pp. 6–9.
27. GOST 9.302–88. Unified system of corrosion and aging protection. Metal and non-metal inorganic coatings. Control methods. Introduced: 01.01.1990.
28. Abrashov А. А., Grigoryan N. S., Aleshina V. Kh., Shloma О. А. Black protective molybdate coatings obtained on galvanized steel. Tsvetnye Metally. 2022. No. 9. pp. 22–27.
29. Aleshina V. Kh., Grigoryan N. S., Asnis N. A., Abrashov A. A. et al. Effect of organic additives on copper electrodeposition in the manufacture of printed boards. International Journal of Corrosion and Scale Inhibition. 2023. Vol. 12, Iss. 1. pp. 126–144. DOI: 10.17675/2305-6894-2023-12-1-7
30. Shawki S., Mikhail S. Black nickel coatings for solar collectors. Mater. Manufact. Process. 2000. Vol. 15, Iss. 2. pp. 737–746.
31. Sidelnikova S. P., Yushchenko S. P., Dikusar А. I. Morphology, structure and composition of coatings during the electrodeposition of "black nickel". Elektronnaya obrabotka materialov. 2009. No. 4. pp. 93–101.