Effect of Cetrimonium Bromide As an Additive on the Morphology and Mechanical Properties of the Electrodeposited Coatings Developed from Ethaline-Based Cyanide-Free Bath

In the present study, a non-aqueous ethaline-based electroplating bath was prepared without the addition of cyanide complexing agents. Gold coatings were prepared via DC galvanostatic route from the developed bath with and without the presence of cetrimonium bromide (CTAB) as an additive. Electrochemical studies (EIS and LSV) provided a detailed insight regarding the metal-complex interaction and the reduction occurring during the electrodeposition process. A time-dependant UV-Vis spectroscopy was carried out to study the stability of the developed bath. Glancing-angle incidence (GI) XRD and EDS analysis of the developed coatings substantiated the presence of pure gold, without any complex. The coatings deposited with the presence of additive had a relatively higher concentration of gold as compared to the coatings without any additive. The SEM and AFM studies were carried out to study the effect of CTAB on the morphology of the coatings. The coatings deposited from the bath containing CTAB had a smooth surface and the AFM studies indicated that they had a low roughness. The coating thickness was confirmed from cross-section SEM. Coatings deposited with the presence of CTAB had a hardness value of 293±6 VHN and those carried out without CTAB showed a lower hardness of 214±9 VHN. The coating deposited with the presence of CTAB was compact, had a bright golden appearance and a good adherence with the underlying substrate. The gold coatings deposited without the presence of CTAB had a dull appearance and the coatings lacked uniformity. The preliminary adherence of the coatings was evaluated using the scotch-tape pull-out test. Fig. SEM micrographs of coating deposited via DC galvanostatic route from ethaline-based gold electroplating bath (a) without CTAB, and (b) with CTAB. Figure 1