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

S. L. Sinebryukhov, Assistant Professor, Head of Laboratory of Unsteady Surface Processes
A. S. Gnedenkov, Junior Researcher (Laboratory of Unsteady Surface Processes), e-mail: asg17@mail.com
D. V. Mashtalyar, Senior Researcher (Laboratory of Biomedical Composite Coatings)
S. V. Gnedenkov, Professor, Deputy Director for Science, Head of Department of Electrochemical Systems and Surface Modification Processes

There was developed the method of formation of composite inhibitor-containing coatings with self-healing properties on magnesium alloys' surface. Obtained experimental results indicate the anti-corrosion properties of samples with composite inhibitor-containing coating on the surface, increased in comparison with the samples without coating and base coating, obtained by plasma electrolytic oxidation method (PEO). The value of current density for self-healing coating depends on the type of treated alloy. At the average, this value is by three magnitude orders higher in contrast to the corresponding value for the sample without coating. The values of impedance modulus for MA8 magnesium alloy with coating are 1,70·10⁵ Ohm·cm², which is by two magnitude orders higher than the same values for the samples without coating. The impedance modulus for the samples with inhibitor-containing coatings after potentiodynamic polarization is decreased, but is still two magnitude orders higher. Electrochemical parameters of porous and porousless layers at the sample surface were calculated before and after polarization due to experimental impedance data modeling by means of equivalent electrical circuits. According to the results of electrochemical modeling, total resistance of basic PEO-coating after potentiodynamic polarization was decreased by more than 30 times (from 2,9·104 Ohm·cm² to 8,6·102 Ohm·cm²), while the value of this parameter for the composite inhibitor-containing coating did not virtually change (3,2·104 Ohm·cm² before polarization, and 2,9·104 Ohm·cm² after polarization). This effect testifies to the presence of additional protective properties of composite coating, revealing under sufficient corrosion influence of environmental factors and preventing the intense material destruction. The obtained value of the sample corrosion rate with self-healing coating is lower (in comparison with sample without coating) and is 17% lower in contrast to the sample with base PEO-layer.

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14. Zhao M. C., Schmutz P., Brunner S., Liu M., Song G., Atrens A. An exploratory study of the corrosion of Mg alloys during interrupted salt spray testing. Corrosion Science. 2009. Vol. 51. pp. 1277–1292.
15. 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.