Institute of Chemistry of Far Eastern Branch of Russian Academy of Sciences, Vladivostok, Russia:

S. V. Gnedenkov, Deputy Director, Head of Department of Electrochemical Systems and Surface Modification Processes
V. S. Egorkin, Senior Researcher of Nonstationary Surface Processes Laboratory, e-mail: egorkin@ich.dvo.ru
S. L. Sinebryukhov, Head of Nonstationary Surface Processes Laboratory
I. E. Vyaliy, Post-Graduate Student (Nonstationary Surface Processes Laboratory)

Aluminum alloy was preliminary subjected to plasma electrolytic oxidation (PEO) and additional treatment (either in ethanol solution or under UV-radiation in the presence of ozone plasma) with subsequent deposition of hydrophobic agent (methoxy-{3-[(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoroctyl)oxy]propyl}-silane solution in decane). Properties of hydrophobic layers on this alloy were researched, and methods of their formation were developed. Plasma electrolytic oxidation of AMg3 (АМг3) samples was carried out in tartrate-containing electrolyte in unipolar polarization mode with 50% polarizing signal duty cycle. Electrochemical properties of obtained coatings were studied using electrochemical impedance spectroscopy and potentiodynamic polarization in 3% NaCl solution. It was found, that the formed composite layers possess hydrophobicity (contact angle is higher than 157^o) and high anticorrosion properties (impedance modulus (|Z|_{f = 0,01 Hz}) ranges from 9,2·10⁹ to 3,4·10¹⁰ Оhm·cm²) in comparison with untreated PEO-coating (35,9±2,9^o; |Z|_{f = 0,01 Hz} = 1,4·108 Оhm·cm²) and aluminium alloy (|Z|_{f = 0,01 Hz} = 2,9·10⁴ Оhm·cm²). Maximum values of contact angles (up to 160,1^o) and minimum values of corrosion current density (1,9·10^–12 A/cm²) belong to the layers, formed by precipitation of hydrophobic agent from solution on the surface of PEO-coating, additionally treated with ethyl alcohol.
This work was carried out with the support of Russian Scintific fund (№ 14-33-00009) and the Government of Russian Federation (Federal agency of scientific organizations).

1. Gnedenkov S. V., Sinebryukhov S. L., Mashtalyar D. V., Egorkin V. S., Sidorova M. V., Gnedenkov A. S. Composite polymer-containing protective coatings on magnesium alloy MA8. Corrosion Science. 2014. Vol. 85. pp. 52–59.
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3. Rudnev V. S., Yarovaya T. P., Nedozorov P. M., Ustinov A. Yu., Tyrina L. M., Malyshev I. V., Kuryavyi V. G., Egorkin V. S., Sinebryukhov S. L., Gneden kov S. V. Obtaining ZrO₂ + CeO_x + TiO₂ /Ti Compositions by Plasma Electrolytic Oxidation of Titanium and Investigating Their Properties. Protection of Metals and Physical Chemistry of Surfaces. 2011. Vol. 47, No. 5. pp. 621–628.
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