Composite Coating

Galvanic coatings have been attracting attention for many years as an object of research from both theoretical and practical points of view. A relatively new direction in electroplating is the production of composite coatings, which are based on metal matrices and dispersed phases of different nature. Introduction to the electrolyte for joint electrochemical deposition of micro -, nanoparticles of oxides, carbides, nitrides, polymers, etc. allows you to adjust the structure, com-position, properties of coatings, providing them with new characteristics. As shown by the analy-sis of publications on this topic in the VINITI RAS Database, systematic research in this area has been carried out for about twenty years and interest in them has not decreased. The system of queries from the array of published documents selected and summarized all currently known combinations of metal matrix/dispersed phase and information about their properties (corrosion behavior, wear resistance, microhardness, resistance to high-temperature oxidation, heat re-sistance, structural and adhesive characteristics). The results are presented in the form of tables and are provided with links to the original works. The analysis of the obtained problem-oriented database showed that for the period 2000-2019, no more than 15-20% of possible combinations were described, and an even smaller number of composite coatings were studied in depth and brought to practical use. The presented material makes it possible to analyze promising areas of research in a clear and easy to find source information form. The review is based on more than 400 references to journal articles. The original database on composite electroplating contains 1650 sources (patents, reports, brief reports, deposited manuscripts, etc.) that may be of interest as an extensive reference material.

Two materials, polyaniline (PANI) and titanium nitride (TiN), used for bipolar plate (BPP) coatings have each shown promise in improving the corrosion resistance and contact resistance, respectively, of metallic bipolar plates. Polyaniline was shown to provide a barrier for the bipolar plate and to effectively lower the corrosion currents observed in ex situ corrosion tests. However, the interfacial contact resistance (ICR) between poly-aniline coatings and gas diffusion layer (GDL) is high and results in high electrical losses. On the other hand, TiN is reported to achieve good conductivity and in some cases improved corrosion resistance. The two materials have also been investigated together in a composite coating and showed promising results, but the contact resistance of the coating was still too high for use in a commercial fuel cell. In this study, the application of an additional layer of TiN over the TiN-polyaniline composite coating (a bilayer coating) is investigated. Composite bilayered PANI TiN coatings were deposited upon SS316L substrates. The optimized coating achieved U.S. Department of Energy (DoE) targets with potentiostatic corrosion currents of~0.024 μA cm-2 and ICR values of 11.2 mΩ cm 2. PANI polymerization was confirmed , using Fourier-transform infrared (FTIR) spectroscopy and TiN loadings were investigated with energy dispersive X-ray (EDX) spectroscopy.