Effects of a N,N-dimethyl-N-2-propenyl-2-propene-1-ammonium chloride-2-propenamide copolymer on bright nickel plating

In this study, the effects of the surfactant N,N-dimethyl-N-2-propenyl-2-propene-1-ammonium chloride-2-propenamide (polyquaternium-7, PQ7), which is used for the first time in nickel bath, on plating rate, particle dimension and leveling effect were studied with electrochemical methods (linear voltammetry and impedance) surface analysis methods (Scanning electron microscopy (SEM) and X-ray diffractometer (XRD)) compared to propargyl alcohol (PA), pyridinium propyl sulfobetaine (PPS) and butyndiol ethoxylate (BEO). According to voltammetric results increase in peak intensity in the presence of PQ7 shows that, plating rate can be improved which is also supported with the decrease in the charge transfer resistance (Rct) obtained from the EIS measurements. According to the SEM results, it was found that PQ7 was the molecule which decreases particle dimensions the most and thus increases leveling the most. While BEO, PA and PPS molecules decrease particle dimension when concentration increases, PQ7 increases it and this molecule exhibited the smallest particle dimension and the most leveling at the lowest concentration. XRD results show that in the case of PQ7 molecule, the lowest peak intensity was obtained at the lowest concentration. Since the peak intensity of the XRD signal is related to particle size, this result also suggested the smallest particle size was obtained in the presence of PQ7 similarly to the SEM result. Thus, PQ7 molecule shows the effect expected from electroplating baths at low concentrations better compared to others. PQ7 enables existing nickel baths to be made up at lower costs and to be more durable due to use of this molecule as additive at very low concentration.

► Polyquaternium (PQ7) was firstly used for nickel electroplating as an organic additive.
► PQ7 results the smallest particle size and the brightest surfaces at low concentration.
► Low-concentration of PQ7 increases the durability of bath and decreases the cost.
► Thus, PQ7 is a feasible alternative to currently popular organic plating additives.