Improved corrosion behavior of nanocrystalline zinc produced by pulse-current electrodeposition

Electrocrystallization in pulse electrolysis

Fundamental aspects of pulsating current metal electrodeposition I: The effect of the pulsating current on the surface roughness and the porosity of metal deposits

It has been known for a relatively long time that the application of a periodically changing current in plating practice leads to improvements in the quality of electrodeposits. Three types of current variation have been found useful: reversing current (RC); pulsating current (PC); and sinusoidal, alternating current superimposed on a direct current (AC).1–12 In recent years, the beneficial effects of pulsating overpotential (PO) have also been discussed.4 Even though this kind of electrodeposition at a periodically changing rate (EPCR) is important from a theoretical point of view and offers a variety of experimental possibilities, it is as yet not frequently used in plating practice.

Theory of the Effect of Electrodeposition at a Periodically Changing Rate on the Morphology of Metal Deposits

The impact of plating parameters on the porosity of cobalt hard gold electrodeposited from a cyanide bath is presented Both constant current and pulsed current deposition were studied by electrochemical and microscopy methods As observed previously, pores tend to decorate grain boundaries, defects, and other morphology features Focused ion beam scanning electron microscopy indicates that perhaps only a small fraction of pores seen on the surface of the ~350 nm thick gold film extends to the electroplated Ni underlayer The density of pores depends on morphology and current efficiency, both of which were found to vary significantly with plating conditions Faceted surface features correlate with a higher pore density For a similar morphology, the pore density increases with the hydrogen generation rate, estimated from current efficiency measurements Pulse plating conditions, with relatively high peak current and frequency, result in deposits with lower porosity due to the capability of generating finer grains while influencing hydrogen evolution rates

Effect of Morphology and Hydrogen Evolution on Porosity of Electroplated Cobalt Hard Gold

The porosity of copper deposits on steel obtained by constant and pulsating overpotential electrolysis has been investigated and determined as a function of the overpotential of deposition. Optimal conditions for copper plating on steel from pyrophosphate baths have been established.

The effect of the overpotential of deposition on the porosity of metal deposits

Measurements of the porosity of nickel deposits on steel, obtained by pulsating potential electrolysis, have been performed. The porosity of the nickel deposits and the effective overpotentials have been determined as a function of frequency of pulsating potential for selected values of effective current densities. A qualitative discussion of the effect of pulsating potential on the porosity of metal deposits has been presented and the optimum electrolysis conditions have been established.

D. N. Keča

Papers

The effect of the overpotential of deposition on the porosity of metal deposits

The effect of pulsating potential electrolysis on the porosity of metal deposits