Microstructure and composition of pulse plated Re–Ni alloys on a rotating cylinder electrode

• The control mechanism for Re deposition is dependent on pulse parameters.
• Pulse plating can be used to tune Ni–Re alloys to a specific application.
• When under activation control, the Re content in the alloy was dependent on Cit:Ni.
• XPS supports our previous mechanism for Ni–Re deposition in d.c. conditions.
• XRD suggests pulse plating forms an hcp Ni–Re phase.

The effect of pulse electrodeposition parameters on the composition and microstructure of Ni–Re alloys were studied on a rotating cylinder electrode. Ni–Re alloys were deposited from a citrate bath where the nickel-to-rhenium ratio was 45:1. The composition of the deposited alloy was monitored by energy dispersive spectroscopy (EDS) and compared to a single component transport-based model describing the pulse limiting current of perrhenate. At long pulse times and high duty cycles, the partial current density of rhenium is predicted by the model, and rhenium inclusion into the alloy can therefore be described as being completely transport controlled. At shorter pulse times and low duty cycles, rhenium deposits under mixed or activation control. The morphology of the surface and cross-section were studied by SEM. The oxidation states and phases were studied by XPS and XRD, respectively, and discussed in view of the pulse parameters. By examining the effect of pulse parameters on composition and microstructure, we can deduce the practical range of pulse parameters for use in Ni–Re alloy film synthesis from dilute perrhenate electrolytes.