Electrodeposition and characterisation of thin layers of NiCo alloys obtained from dilute chloride baths

Synthesis and Properties of Electrodeposited Ni–Co/WS2 Nanocomposite Coatings

Ni–Co coatings have gained widespread attention due to their potential in replacing hard chromium deposits (which have traditionally utilized toxic and corrosive chromic acid baths). A major challenge is to lower the high coefficient of friction of coated surfaces against steel, under dry sliding conditions. In this research, low friction Ni–Co/WS2 nanocomposite coatings have been prepared by a convenient, one-pot electrodeposition from aqueous Ni–Co plating baths containing WS2 particles. The embedment of the WS2 lubricants is found to reduce the friction coefficient of coating significantly, and an ultra-low friction coefficient of 0.16 is obtained for the coating having a WS2 content of 7.1 wt.%. Morphology and composition characterization of wear tracks reveal that the formation of a WS2-rich lubricating tribofilm on the contact surfaces is beneficial to a low friction coefficient and good oxidation resistance. The wettability of electrodeposited coatings was also investigated. Compared to pure Ni-Co coating, the Ni–Co/7.1 wt.% WS2 coating has an excellent hydrophobicity with a high water contact angle (WCA) of 157°, due to a rough surface with dual scale protrusions and the low surface energy of WS2.

Microstructure and Corrosion Behavior of Electrodeposited NiCo, NiZn and NiCu Nanocrystalline Coatings in Alkaline Solution

The present paper deals with evaluation of corrosion behavior of electrodeposited nanocrystalline (Nc) NiCo, NiZn and NiCu alloys. Nc NiCo, NiZn and NiCu coating electrodes were electroplated from sulfate electrolyte on copper foil by the galvanostatic technique and ultrasound waves. The chemical composition, surface morphology and crystalline structure of the different alloys were studied using energy dispersive spectroscopy, scanning electron microscope and X-ray diffraction methods. The electrochemical behavior of the deposited material in 1.0 M KOH solutions was investigated. The electrochemical behavior of the coating electrodes in alkaline solutions was investigated by potentiodynamic polarization techniques and electrochemical impedance spectroscopy (EIS). Results showed that the alloying of nickel with Co causes an increase in the stability of Ni–alloy in alkaline solutions in comparison to Ni–Cu and Ni–Zn alloys. The corrosion resistance values of Ni–Zn coatings were lower compared to those of the other investigated alloy coatings due to preferential dissolution of Zn from the matrix. The experimental impedance data were fitted to theoretical data according to a proposed equivalent circuit model representing the electrode/electrolyte interface.