Electrodeposition of SnBi coatings based on deep eutectic solvent

Tin–bismuth (SnBi) alloy coatings were satisfactorily electrodeposited on copper electrodes from a choline chloride–ethylene glycol deep eutectic solvent containing BiCl₃, ZnCl₂ and H₃BO₃. The electrochemical feature of the electrolyte system was inspected via linear sweep voltammetry. The results indicated that the SnBi alloy coating was codeposited as the deposition potential was prolonged up to the potential range, leading to the inadequate deposition of zinc on the copper electrode. Dendrite formation, simple eutectics and diversification of grain size were studied through the results of the morphology and structure analyses. The X-ray diffraction results demonstrated an increasing grain size of Bi and an opposite trend of Sn when the potential increased. The relevance of the Bi at% of the codeposited BiSn on the deposition potential, temperature and Bi(II) molar ratio was investigated. The results indicated the possibility of electroplating the SnBi alloys with their composition around the eutectic point.