LAUSR

Abstract The effect of thermally and electrically conductive TiB2, ZrB2 and TiC particles on the stability of high phosphorus electroless nickel (EN) plating bath was studied through particle surface modifications. The EN composite coatings with optimal contents of the hard particles were deposited on carbon steel substrates, characterized in microscopic morphology and composition (optical microscope, SEM/EDS), crystallinity (XRD), and micro-hardness. The composite coatings were evaluated with erosion and corrosion tests. The results showed that the electrically conductive hard particles affect the stability of EN plating bath in the order of TiB2 > TiC > ZrB2, with the utmost impact from TiB2 and insignificance from ZrB2. The incorporation of TiB2 particles trigged a rapid decomposition of an EN plating bath within 2 h, which is likely due to the high catalytic activity of TiB2 particles. The nickel phosphorus (NiP) matrix composite coatings are able to offer a combination of wear and corrosion resistance to effectively protect carbon steel components from corrosion according to the test results, which supports an expectation that the coatings can be used in harsh environments, e.g., those encountered in marine and oil and gas (O&G). The effect of heat treatment on the coating properties, in particular, corrosion and wear resistance were studied and the mechanisms behind the property changes were discussed as well.