Metal matrix composite (MMC) and nanocomposite coatings are being proposed as alternatives to their monolithic counterparts to improve protection against wear in chemically-aggressive environments. Corrosion resistance of MMC coatings is strongly dependent on the coating microstructure, which is affected by the physical and chemical nature of the dispersed particles, as well as the particle concentration. In this paper, we present the results of our tests on the corrosion response of Ni-P MMC coatings with micro-crystalline and nano-crystalline diamond as the dispersed phase. Potentiodynamic and electrochemical impedance spectroscopy tests were performed to compare the corrosion of Ni-P composites and nanocomposites, and the results are analyzed in terms of their microstructures. The corrosion potential is primarily determined by the P content and the heat treatment carried out after deposition, and is weakly dependent on the particle content. In low-P coatings, the presence of micrometer-size particles has no significant impact on Ecorr and Icorr. Heat treatment increases Ecorr and decreases Icorr. Similar trends are observed in the high-P coatings. EIS results suggest self-healing behavior with some microstructures.

Subject
Nickel coatings, Electrochemical impedance spectroscopy, Coatings, Materials, Diamond, Microstructure, Phosphorus, Composites, Nanocomposites, Heat, Corrosion resistance, Polarization resistance, Heat treatment
Keywords:
Electroless Ni-P, nanocomposites, diamond
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2017
Association for Materials Protection and Performance (AMPP)
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