Nickel electrodeposition: the influence of brighteners on the incorporation of sulphur and carbon in nickel layers – measurement of sulphur and carbon content with glow discharge optical emission spectroscopy

The electrochemical behaviour of various brighteners during nickel deposition and their influence on the composition of nickel electrodeposits is presented. The focus is on the simultaneous application of various pyridinic and acetylenic brighteners in combination with saccharin, with emphasis on their interactions and effects on sulphur and carbon incorporation into the nickel coatings. Sulphur and carbon were analysed using glow discharge optical emission spectroscopy. The brighteners were analysed by HPLC coupled with a mass spectrometric detector and a diode-array detector. Pyridinic and acetylenic brighteners accelerate the cathodic conversion of saccharin. Consequently, the increased conversion rate of saccharin to sulphur-free products is also associated with sulphur and carbon incorporation into the nickel deposits (sulphur increases from 0.02 to max. 0.15 wt.%). The results reveal differences in the effects of both brighteners on sulphur and carbon incorporation. Pyridinic brighteners enhance sulphur and carbon incorporation, whereas acetylenic brighteners, at higher concentrations, decrease it.