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

D. V. Mashtalyar, Senior Researcher; Laboratory of Composite Coatings for Biomedical Applications, е-mail: chemi@ich.dvo.ru
S. V. Gnedenkov, Dep. Director for Science; Head of the Department of Electrochemical Systems and Surface Modification Processes
S. L. Sinebryukhov, Associate Professor; Head of Laboratory of Nonstationary Surface Processes
K. V. Nadaraia, Junior Researcher; Laboratory Nonstationary Surface Processes

Today one of the most common methods of the coatings formation on titanium alloys is a thermal oxidation. Along with the merits, this method of surface modification has certain drawbacks: high energy and labor costs, lack of the possibility of restoration of the coatings after damage during exploitation, high probability of manufacturing defects formation. The importance of the above problems for the practice, as well as the increasing demands on the quality of the protective layers formed on metals and alloys indicates the relevance of the task of scientific search for alternative ways of formation and restoration the protective properties of coatings on products that have been in exploitation. This paper presents the results of investigation of plasma electrolytic oxidation modes of commercial pure titanium VT1-0 with an oxide layer on the surface, providing restoration of the protective performances of the coating, the integrity of which was destroyed during operation. The combination of plasma electrolytic oxidation and the subsequent application of a fluoropolymer material by dipping in the suspension of superdispersed polytetrafluoroethylene (SPTFE) and thermal treatment at 315 ^oC for 10 minutes allowed the formation of practically significant composite polymer-containing coating. Evaluation of the data obtained by the potentiodynamic polarization method indicates a decreasing the corrosion current density and an increasing the polarization resistance by more than three times for the formed composite coatings in comparison with the coating obtained using only plasma electrolytic oxidation treatment of samples with thermal oxide on the surface. Composite layers reliably protect products made of steel and copper-based alloys against galvanic corrosion at contact with titanium alloys in seawater. The technology of restoring the protective properties of the coating, the barrier layer of which was destroyed during the exploitation, was implemented in "Far East Shipyard "Zvezda" at the end of 2015.

This work was supported by the Russian Science Foundation (project No. 14-33-00009).

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