A comprehensive review of various non-cyanide electroplating baths for the production of silver and gold coatings

ABSTRACT

Cyanide-based baths are generally used industrially to produce silver and gold coatings via electroplating. Baths containing ([Au(CN)₂]⁻) and ([Ag(CN)₂]⁻) are used for the deposition of gold and silver coatings, respectively. However, due to the severe toxicity, the technical personnel involved in work are at risk. Additionally, the disposal of cyanide-containing wastes poses a significant threat to the environment as they pollute various natural resources. The coatings produced from alkaline cyanide-based baths cause embrittlement of electronic circuit patterns. Due to these reasons, many cyanide-free baths have started to replace the existing cyanide-based baths. In the cyanide-free baths, the primary cyanide complexing agent is replaced with eco-friendly alternative compounds like sulphite, thiosulphate, thiourea, DMH, EDTA, and ionic liquids (ILs). This review article provides an overview of the various cyanide-free electroplating baths available for electroplating silver and gold that are either used for commercial practice or are developed for laboratory-scale use.

GRAPHICAL ABSTRACT

KEYWORDS:

• Cyanide-free
• gold plating
• silver plating
• electrodeposition
• environmental-friendly
• thiosulphate bath
• sulphite bath
• cyanide-free complexing agents

Acknowledgements

The authors have used Origin, MS Office, and Bio Render for creating schematics/illustrations used in this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

K.D. and S.D would like to acknowledge the funding from the Ministry of Education (Formerly, Ministry of Human Resource and Development), Government of India, for the project code UAY_IITKGP_002 (Phase II, BBN), with approval order number File No. 35-8/2017-TS.1, dated 05-12-2017, to carry out the work. B.S. and S.J. would like to acknowledge the Ministry of Education (Formerly, Ministry of Human Resource and Development), Government of India, for their Doctoral Fellowship.