DOI: https://doi.org/10.32515/2664-262X.2023.8(39).1.20-27

Study of the Influence of the Temperature of the Electrolyte During Pulse Anodization on the Properties of the Surface Layers of Technical Aluminum

Volodymyr Hvozdetskii, Sergiy Markovych, Khrystyna Zadorozhna, Mykhajlo Student

About the Authors

Volodymyr Hvozdetskii, Senior Researcher, PhD in Technics (Candidate of Technics Sciences), Karpenko Physico-Mechanical Institute of NAS of Ukraine, Lviv, Ukraine, e-mail: gvosdetcki@gmail.com

Sergiy Markovych, Associate Professor, PhD in Technics (Candidate of Technics Sciences), Central Ukrainian National Technical University, Kropivnitskiy, Ukraine, e-mail: marko60@ukr.net, ORCID ID: 0000-0003-1393-2360

Khrystyna Zadorozhna, Researcher, PhD in Technics (Candidate of Technics Sciences), Karpenko Physico-Mechanical Institute of NAS of Ukraine, Lviv, Ukraine, e-mail: 880988@ukr.net, ORCID ID: 0000-0002-1310-6467

Mykhajlo Student, Senior Researcher, Doctor in Technics (Doctor of Technic Sciences), Karpenko Physico-Mechanical Institute of NAS of Ukraine, Lviv, Ukraine, e-mail: student.phmi@gmail.com, ORCID ID: 0000-0002-5992-5898

Abstract

luminum alloys are characterized by low abrasive wear resistance, which significantly restricts their wide use in technological environments, especially if they contain abrasive particles. The method of pulse anodizing, which consists in periodically changing the current density, allows to improve the hardness and abrasive wear resistance. However, the influence of temperature on these processes has not been sufficiently studied. The process of pulsed hard anodizing was carried out in a 20% aqueous H2SO4 solution at a current density of 1.4 A/dm2 with a frequency of 100 Hz and a sparability of 75%. The temperature of the electrolyte during the formation of layers was maintained at -5°±1С, 0°С±1, +5°С±1, +10°С±1. The duration of synthesis was 60 minutes. At low temperatures of less than -5С due to the low speed of electrochemical processes, oxide layers with reduced microhardness and thickness are synthesized. At the same time, the phase analysis recorded the synthesis of an oxide layer based on aluminum with the content of two phases: the synthesis of the anodized layer begins with the formation of hydrated aluminum oxide Al2O3•H2O. As the anodizing temperature increases, the rate of electrochemical processes increases, which leads to an increase in the thickness of the anodized layer and its microhardness. At temperatures of 0С and -5С, the anodized layer contains only one phase - Al2O3 H2O, (boehmite) with one water molecule. At anodizing temperatures of +5С and -8С, the anodized layer is formed again in the form of two phases - Al2O3 3H2O (gibbsite) and Al2O3H2O (boehmite) and at a temperature of +10С only Al2O3 3H2O (gibbsite). At a temperature lower than –10°C, the electrolyte turns into a gel-like substance in which electrochemical reactions practically stop, so the synthesis of a pulsed solid anodized layer at a temperature of –5°C was started. However, as a result of the synthesis at T = –5 С and then even higher (up to 0С), the average thickness of the pulsed hard anodized layer increased from 83 μm to 110 μm. With further increase in the temperature of the electrolyte, the thickness decreased and at an electrolyte temperature of +10 С it was 80 μm. Such a change in the thickness of the anodized layer depending on the synthesis temperature was explained by two opposing processes that occur during anodization. As the temperature of the electrolyte increases, the process of synthesis of the layer intensifies first of all, and therefore the thickness of the obtained layer should constantly increase with the increase of the synthesis temperature. However, an increase in the temperature of the electrolyte also intensifies the surface dissolution of the anodized layer, which is aimed at reducing the thickness of the anodized layer. And when the rate of dissolution of the anodized layer begins to exceed the rate of its synthesis, its thickness begins to decrease. Conclusions: 1) The more water and sulfur molecules in the anodized layer, the lower its microhardness and abrasive wear resistance. 2) The minimum wear of the anodized layer, which means the highest wear resistance, was recorded for layers synthesized at an anodization temperature of -8ºС, and the maximum wear and lowest wear resistance at an anodization temperature of -5ºС. 3) High wear resistance of anodized layers synthesized at electrolyte temperatures from -8 to +10ºС under conditions of friction without lubrication is caused by the presence of crystalline water in the anodized layer.

Keywords

aluminum alloys, pulse anodizing temperature, structure, hardness, wear resistance

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References

1. Junghoon Lee, Yonghwan Kim, Heuiun Jang, Uoochang Jung and Wonsub Chung (2011). Cr2O3 Sealing of Anodized Aluminium Alloy by Heat Treatment. Procedia Engineering, 10, P. 2803–2808 [in English]

2. Ivasenko, I.B., Zadorozhna, Kh.R., Posuvailo, V.M. et al. (2019). Otsinka rozpodilu vkliuchen i defektiv plazmoelektrolitnykh i lazerno modyfikovanykh pokryttiv na aliuminiievykh splavakh [Evaluation of the distribution of inclusions and defects of plasma-electrolyte and laser-modified coatings on aluminum alloys] . Naukovi notatky : Mizhvuzivskyi zbirnyk  Scientific notes: interuniversity. coll, Vol. 66, 135–140 [in Ukrainian]

3. Pylypenko, O.I. (Eds.). (2016). Elektrokhimichne oksyduvannia aliuminiiu i yoho splaviv : Metodychni vkazivky do laboratornoi roboty dlia studentiv spetsialnosti «Tekhnichna elektrokhimiia» dennoi ta zaochnoi form navchannia [Electrochemical oxidation of aluminum and its alloys: method. directions to the lab. do for full-time and part-time students of the "Technical Electrochemistry" specialty] . Kharkiv : NTU «KhPI» [in Ukrainian]

4. Shih, H. & Tzou, S. (2000). Study of anodic oxidation of aluminum in mixed acid using a pulsed current. Surface and Coatings Technology. 124, P. 278–285 [in English]

5. Stoiev, P.I., Lytovchenko, S.V., Hirka, I.O. & Hrytsyna, V.T. (2019). Khimichna koroziia ta zakhyst metaliv [Chemical corrosion and protection of metals]. Kharkiv : KhNU imeni V. N. Karazina [in Ukrainian]

6. Li-Rong Zhao, Jian Wang, Yan Li, Cheng-Wei Wang, Wei-Min Liu. (2010). Anodic aluminum oxide films formed in mixed electrolytes of oxalic and sulfuric acid and their optical constants / Physica B: Condensed Matter, 405, №11, P.456-460 [in English]

7. Kwolek P., Krupa K., Obłój A., Kocurek P., Wierzbińska M. & Sieni J.. (2018). Alloy in the hard anodizing process / Journal of Materials Engineering and Performance, 27, P. 3268–3275 [in English]

8. Student, M.M., Hvozdetskyi, V.M., Veselivska, H.H. et al. (2021). Vplyv skladu elektrolitu na kharakterystyky syntezovanoho pid chas tverdoho anoduvannia aliuminiiu oksydnoho sharu [Influence of the electrolyte composition on the characteristics of the oxide layer synthesized during hard anodization of aluminum]. Tsentralnoukrainskyi naukovyi visnyk. Tekhnichni nauky – Central Ukrainian scientific bulletin. Technical sciences, Issue 4 (35), 63–69 [in Ukrainian]

9. Veselivska, H.H., Sirak, Ya.Ya., Hvozdetskyi, V.M. et al. (2017). Znosostiikist ta koroziina tryvkist PEO shariv na pokrytti zi splavu D16 [Wear resistance and corrosion resistance of PEO layers on D16 alloy coating] . Konstruiuvannia, vyrobnytstvo ta ekspluatatsiia silskohospodarskykh mashyn : zahalnoderzh. mizhvid. nauk.-tekhn. zb  Design, production and operation of agricultural machines: general government. between science and technology coll, Issue 47, part. 2, 31-37 [in Ukrainian]

10. Student, M.M., Pokhmurska, H.V. & Hvozdetskyi, V.M. et al. (2018). Bahatofunktsionalni elektroduhovi pokryttia [Багатофункціональні електродугові покриття]. Lviv : Prostir-M [in Ukrainian]

Citations

  1. Cr2O3 Sealing of Anodized Aluminium Alloy by Heat Treatment / Junghoon Lee, Yonghwan Kim, Heuiun Jang, Uoochang Jung and Wonsub Chung. Procedia Engineering. 2011. 10. P. 2803–2808.
  2. Оцінка розподілу включень і дефектів плазмоелектролітних і лазерно модифікованих покриттів на алюмінієвих сплавах / І.Б. Івасенко та ін. Наукові нотатки: міжвуз. зб., 2019. Вип. №66. С. 135–140.
  3. Електрохімічне оксидування алюмінію і його сплавів: метод. вказівки до лаб. роб. для студентів спеціальності «Технічна електрохімія» денної та заочної форм навчання / уклад.: О.І. Пилипенко. Х. : НТУ «ХПІ», 2016. 36 с
  4. Shih H., Tzou S. Study of anodic oxidation of aluminum in mixed acid using a pulsed current. Surface and Coatings Technology. 2000. 124. P. 278–285.
  5. Хімічна корозія та захист металів : навчальний посібник / П. І. Стоєв та ін. Х. : ХНУ імені В. Н. Каразіна, 2019. 216 с
  6. Anodic aluminum oxide films formed in mixed electrolytes of oxalic and sulfuric acid and their optical constants / Li-Rong Zhao, Jian Wang, Yan Li, Cheng-Wei Wang, Wei-Min Liu. Physica B.: Condensed Matter. 2010. 405. №11. P.456-460
  7. Alloy in the hard anodizing process / P. Kwolek, K. Krupa, A. Obłój, P. Kocurek, M. Wierzbińska, J. Sieni. Journal of Materials Engineering and Performance. 2018. 27. P. 3268–3275
  8. Вплив складу електроліту на характеристики синтезованого під час твердого анодування алюмінію оксидного шару / М.М. Студент та ін. Центральноукраїнський науковий вісник. Технічні науки : зб. наук. пр. 2021. Вип. 4 (35). С. 63–69.
  9. Зносостійкість та корозійна тривкість ПЕО шарів на покритті зі сплаву Д16 / Г. Г. Веселівська та ін. Конструювання, виробництво та експлуатація сільськогосподарських машин : загальнодерж. міжвід. наук.-техн. зб. 2017. Вип. 47, ч. 2. С. 31-37.
  10. Багатофункціональні електродугові покриття : монографія / М. М. Студент та ін. Львів : Простір-М, 2018. 335 с.
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