Diverse electrodeposits from modified acid sulphate (Watts nickel) baths

Abstract

A diverse range of nickel-based coatings can be cathodically deposited from a classical Watts electroplating bath containing suitable additives by appropriate control over operational conditions. Modern nickel-based electrodeposits are concisely reviewed and can be seen to be longer-term developments from the publication of optimised conditions for rapid nickel plating from an acid sulphate bath by Watts 100 years ago, in 1916. Recent examples of tribological nickel electrodeposits are illustrated by examples from the authors’ laboratory: (i) low friction, hard, wear resistant surfaces (containing 2-D, layered, self-lubricating particles of Ni–P–MoS₂), (ii) superhydrophobic layers of Ni–WS₂, showing a lotus petal effect (for self-cleaning surfaces), (iii) light emitting, luminescent signal bearing surfaces of Ni–BAM (BaMgAl₁₁O₁₇:Eu²⁺) metal oxide, (providing an in-situ phosphor wear tracer) and (iv) nanocrystalline surfaces of Ni, Co, Ni–Co and Ni–Co–P (including high surface area electrocatalysts). Important trends in the deployment of the longstanding, versatile Watts nickel electroplating bath are seen to include the development of (a) surfaces having tailored structure, hence special properties, by choice of bath composition and operational conditions, (b) nanostructured composite layers containing mixed inclusions and (c) layers able to diagnose in-service wear and provide an output signal. Subject areas needing further research are suggested.

Keywords:

• Additives
• Lubrication
• Nanostructure
• Surface tension
• Tribology
• Watts nickel