The effects of additive TN1, power waveforms (full wave, half wave, and direct current), current density and pH on the throwing power of Ni-Co alloy electroforming solution had been investigated by orthogonal tests; and the effects of plating parameters on current distribution of cathode by ANSYS numerical simulation were discussed. The results of orthogonal test showed that the additive TN1 had the largest effect on the throwing power; the power waveform was secondary; the current density and pH had minor effect. The biggest throwing power was 78% when the TN1 was 15g/L and waveform was full wave. Numerical simulation showed that the cathode shape and shield had effect on current distribution; reasonable cathode shape and application of shield could improve the current distribution. The thickness uniformity of part could be up to 92% by optimizing of electrolyte, adjusting the electroforming technics and applying second electroplating.
Zn-Ni alloy coatings were electrodeposited on low carbon steel substrate using a cyanide-free alkaline bath containing tetraethylenepentamine (TEPA) and triethanolamine (TEA) as complexing agents for Ni2+cations. Effect of TEA/Ni2+molar ratio on electrodeposition behavior, micromophology, Ni content and corrosion resistance of coatings were studied by means of SEM/EDS, polarization curve and electrochemical impedance spectroscopy (EIS), respectively. It was found that the deposition potential and elecctrochemical impedance of the cathode sample during the electrodeposition was influenced by the TEA/Ni2+molar ratio (TNmr) in the bath. The deposition potential shifts negatively and the impedance rises with increasing TNmrup to 2. The nickel content in Zn-Ni deposit was varied in a range from 16.81 to 19.04 wt.%. The dependence of cathodic current efficiency and depositing velocity of the coating on TNmrof plating bath were also determined. A fine-grained and smooth-faced coating was obtained at TNmr=2, which exhibited the highest corrosion resistance in 3.5% NaCl environment.
The zinc-nickel alloy coatings were electrodeposited by changing the concentration of the NiSO4 • 6H2O in the plating bath. The scanning electron microscopy (SEM) was used to observe the coating’s surface morphology. The EDS was applied to test the coating’s nickel content. The corrosion resistance was studied by using the Tafel curves, AC impedance spectra and the neutral salt spray test. The results showed that: The coating’s nickel content could reach 12.56% when the NiSO4 • 6H2O concentration was 8g/L in the bath and the coating was very smooth, dense and bright. Its corrosion potential was low and its corrosion reaction resistance was best with red rust time up to 46d, so it had good corrosion resistance. But when the NiSO4 • 6H2O concentration was changed, the coatings’ corrosion resistance would be more or less changed.
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