Characteristics of plasma electrolytic oxidation coatings on 6061 al alloy prepared at different current densities


  • Quang-Phu Tran Department of Electrical and Electronic Engineering, Hung Yen University of Technology and Education, 39A Road, Dan Tien Commune, Khoai Chau District, Hung Yen Province, Viet Nam
  • Van-Da Dao Department of Electrical and Electronic Engineering, Hung Yen University of Technology and Education, 39A Road, Dan Tien Commune, Khoai Chau District, Hung Yen Province, Viet Nam
  • Van-Hoi Pham Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Ha Noi, Viet Nam



plasma electrolytic oxidation (PEO), current density, 6061 Al alloy, micro-hardness, corrosion resistance.


Plasma electrolytic oxidation (PEO) has earned much attention due to its powerful and easy formation of hard and corrosion-resistant oxide layers on valve metals, such as Al alloys. Here we report the effects of current density (CD) on microstructure and properties of coatings on 6061 Al alloy by PEO using direct current mode. The electrolyte contains the chemicals of Na2SiO3, Na2WO4´2H2O, and NaH2PO2´H2O. The CDs adopted 5.0, 7.5, 10.0, and 12.5 A/dm2, respectively, for a fixed PEO time of 30 min. The thickness, surface morphology, phase composition, hardness, and corrosion resistance of PEO coatings as the function of the applied CD have been studied and discussed. Studied results show the coating thickness is proportional to the applied CD. When the applied CD increases 2.5 times from 5.0 to 12.5 A/dm2, the growth rate of oxide layers increased by more than 3.5 times, from 0.423 to 1.493 μm/min, respectively. SEM images are characterized by a reduction in the ratio of agglomerate-bumps-region/flatten-region as applied CD increases. However, cracks and larger pores appear when the applied CD is higher than 10.0 A/dm2. X-ray diffraction pattern shows that the main phases of Al, g-Al2O3, α-Al2O3, and W are contained in all coatings. PEO coated sample has the highest hardness of 1290 HV and highest polarization resistance of 8.80 ´ 106 Wcm2 obtained at applied CD 10 A/dm2 which shows the best performance of the coating. The variation in coating performance is explained by microstructure details, specifically phases, compositions of oxide-layers, and micro-pores and cracks.


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Voevodin A., Yerokhin A., Lyubimov V., Donley M., Zabinski J. - Characterization of wear protective Al2O3SiO2 coatings formed on Al-based alloys by micro-arc discharge treatment, Surface and Coatings Technology, 86 (1996) 516–521. DOI:

Yerokhin A. L., Nie X., Leyland A., Matthews A., Dowey S. J. - Plasma electrolysis for surface engineering, Surface and Coatings Technology, 122 (1999) 73–93. DOI:

Tran Q.-P., Sun J.-K., Kuo Y.-C., Tseng C.-Y., He J.-L., Chin T.-S. - Anomalous layer-thickening during micro-arc oxidation of 6061 Al alloy, Journal of Alloys and Compounds, 697 (2017) 326–332. DOI:

Tran Q.-P., Chin T.-S., Kuo Y.-C., Jin C.-X., Trung T., Van Tuan C., Dang D. Q. - Diamond powder incorporated oxide layers formed on 6061 Al alloy by plasma electrolytic oxidation, Journal of Alloys and Compounds, 751 (2018) 289-298. DOI:

Tran Q.-P., Chin T.-S. - Plasma electrolytic oxidation coating on 6061 Al alloy using an electrolyte without alkali ions, Journal of Science and Technology, 54 (5A) (2016) 151–158. DOI:

Tran Q.-P., Kuo Y.-C., Sun J.-K., He J.-L., Chin T.-S. - High quality oxide-layers on Al-alloy by micro-arc oxidation using hybrid voltages, Surface and Coatings Technology, 303, Part A (2016) 61-67. DOI:

Wu H., Wang J., Long B., Long B., Jin Z., Naidan W., Yu F., Bi D. - Ultra-hard ceramic coatings fabricated through microarc oxidation on aluminium alloy, Applied surface science, 252 (2005) 1545-1552. DOI:

Yang G. L., Lü X. Y., Bai Y. Z., Cui H. F., Jin Z. S. - The effects of current density on the phase composition and microstructure properties of micro-arc oxidation coating, Journal of Alloys and Compounds, 345 (2002) 196–200. DOI:

Hussein R. O., Northwood D. O., Su J. F., Nie X. - A study of the interactive effects of hybrid current modes on the tribological properties of a PEO (plasma electrolytic oxidation) coated AM60B Mg-alloy, Surface and Coatings Technology, 215 (2013) 421–430. DOI:

Wang L., Fua W., Chen L. - Evolution of active species and discharge sparks in Na2SiO3 electrolyte during PEO process, Journal of Alloys and Compounds, 509 (2011) 7652–7656. DOI:

Javidi M., Fadaee H. - Plasma electrolytic oxidation of 2024-T3 aluminum alloy and investigation on microstructure and wear behavior, Applied Surface Science, 286 (2013) 212– 219. DOI:

Khan R. H. U., Yerokhin A. L., Pilkington T., Leyland A., Matthews A. - Residual stresses in plasma electrolytic oxidation coatings on Al alloy produced by pulsed unipolar current, Surface and Coatings Technology, 200 (2005) 1580–1586. DOI:

Wang L., Nie X. - Silicon effects on formation of EPO oxide coatings on aluminum alloys, Thin Solid Films, 494 (2006) 211–218. DOI:

Han I., Choi J. H., Zhao B. H., Baik H. K., Lee I. S. - Changes in anodized titanium surface morphology by virtue of different unipolar DC pulse waveform, Surface and Coatings Technology, 201 (2007) 5533–5536. DOI:

Lv G., Gu W., Chen H., Feng W., Khosa M. L., Li L., Niu E., Zhang G., Yang S. Z. - Characteristic of ceramic coatings on aluminum by plasma electrolytic oxidation in silicate and phosphate electrolyte, Applied Surface Science, 253 (2006) 2947–2952. DOI:

Gao H. T., Zhang M., Yang X., Huang P., Xua K. - Effect of Na2SiO3 solution concentration of micro-arc oxidationprocess on lap-shear strength of adhesive-bonded magnesium alloys, Applied Surface Science, 314 (2014) 447–452. DOI:

Liu X. H., Zhu L. Q., Liu H. C., Li W. P. - Investigation of MAO coating growth mechanism on aluminum alloyby two-step oxidation method, Applied Surface Science, 29 (2014) 12–17. DOI:

Nie X., Meletis E. I., Jiang J. C., Leyland A., Yerokhin A. L., Matthews A. - Abrasive wearycorrosion properties and TEM analysis of Al2O3 coatings fabricated using plasma electrolysis, Surface and Coatings Technology, 149 (2002) 245–251. DOI:

Yazıcı S. K., Muhaffel F., Baydogan M. - Effect of incorporating carbon nanotubes into electrolyte on surfacemorphology of micro arc oxidized Cp-Ti, Applied Surface Science, 318 (2014) 10–14. DOI:

Wang J. H., D M. H., Han F. Z., Yang J. - Effects of the ratio of anodic and cathodic currents on the characteristics of micro-arc oxidation ceramic coatings on Al alloys, Applied Surface Science, 292 (2014) 658–664. DOI:

Shen D. J., Li G. L., Guo C. H., Zou J., Cai J. R., He D. L., Ma H. J., Liu F. F. - Microstructure and corrosion behavior of micro-arc oxidation coatingon 6061 aluminum alloy pre-treated by high-temperature oxidation, Applied Surface Science, 287 (2013) 451–456. DOI:

Long B. H., Wu H. H., Long B. Y., Wang J. B., Wang N. D., Lu X. Y., Jin Z. S., Bai Y. Z. - Characteristics of electric parameters in aluminium alloy MAO coating process, Journal of Physics D: Applied Physics, 38 (2005) 3491–3496. DOI:

Khaselev O., Yahalom J. - The anodic behaviour of binary Mg-Al alloys in KOH aluminate solutions, Corrosion Science, 40 (1998) 1149–1160. DOI:

Gu W. C., Lv G. H., Chen H., Chen G. L., Feng W. R., Yang S. Z. - Characterisation of ceramic coatings produced by plasma electrolytic oxidation of aluminum alloy, Materials Science and Engineering A, 447 (2007) 158–162. DOI:

Wasekar N. P., Jyothirmayi A., Sundararajan G. - Influence of prior corrosion on the high cycle fatigue behavior of microarc oxidation coated 6061-T6 aluminum alloy, International Journal of Fatigue, 33 (2011) 1268–1276. DOI:

Jin F. Y., Chu P. K., Tong H. H., Zhao J. - Improvement of surface porosity and properties of alumina films by incorporation of Fe micrograins in micro-arc oxidation, Applied Surface Science, 253 (2006) 863–868. DOI:

Kaseem M., Kamil M. P., Kwon J. H., Ko Y. G. - Effect of sodium benzoate on corrosion behavior of 6061 Al alloy processed by plasma electrolytic oxidation, Surface and Coatings Technology, 283 (2015) 268–273. DOI:

Khan R. H. U., Yerokhin A., Li X., Dong H., Matthews A. - Surface characterization of DC plasma electrolytic oxidation treated 6082 aluminium alloy: effect of current density and electrolyte concentration, Surface and Coating Technology, 205 (2010) 1679–1688. DOI:

Raj V., Ali M. M. - Formation of ceramic alumina nanocomposite coatings on aluminium for enhanced corrosion resistance, Journal of Materials Processing Technology, 209 (2009) 5341–5352. DOI:

Snizhko L., Yerokhin A., Pilkington A., Gurevina N., Misnyankin D., Leyland A., Matthews A. - Anodic processes in plasma electrolytic oxidation of aluminium in alkaline solutions, Electrochimica Acta, 49 (2004) 2085-2095. DOI:

Stern M., Geary A. L. J. J. o. t. e. s. - Electrochemical polarization I. A theoretical analysis of the shape of polarization curves, 104 (1957) 56-63. DOI:

Sarbishei S., Faghihi Sani M. A., Mohammadi M. R. - Study plasma electrolytic oxidation process and characterization of coatings formed in an alumina nanoparticle suspension, Vacuum, 108 (2014) 12-19. DOI:




How to Cite

Q.-P. Tran, V.-D. Dao, and V.-H. Pham, “Characteristics of plasma electrolytic oxidation coatings on 6061 al alloy prepared at different current densities”, Vietnam J. Sci. Technol., vol. 58, no. 6, pp. 699–708, Dec. 2020.