Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Electroplating of Black Nickel: Bath Age and its Effect on Coating Quality

Zhi Hao Aaron Teo1, Yajuan Sun1, Yujie Zhou1 and Yong Teck Tan1,a

1Singapore Institute of Manufacturing Technology, 2 Fusionopolis Way, Innovis, Singapore 138634


Black nickel coating is commonly electroplated onto various substrates, including ferrous and non-ferrous metals/alloys, as a decorative layer to provide uniform black appearance. In the black nickel-plating process, nickel and zinc are co-plated out of plating bath with different ratios, leading to difficulty and complexity in bath maintenance by using soluble anode. In practice, an inert anode is used with regular replenishment to control the bath composition and pH value in the optimal ranges. Hence, as the plating bath ages and the plating bath composition changes due to the unequal consumption of nickel and zinc, the deposited coating will no longer appear black. Boric acid is frequently used as a pH buffer to stabilize the pH value of the plating bath to produce black coating with minimal bath maintenance. However, disposing the used plating bath is often expensive and incurs environmental damage when not properly disposed. In this work, a boric acid-free black nickel coating process is systematically investigated during electroplating onto copper substrates, in terms of plating bath chemical composition and pH value, on the deposited coating appearance and coating composition, to arrive at a process map indicating suitable process window for optimum black nickel coating.

Keywords: Coating, Electroplating, Bath analysis, Titration, Spectrophotometer, EDX

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