Studies in the Discontinuities of Electrodeposited Metallic Coatings

The porosities of gold electroplates on copper may be determined by measuring the corrosion potentials of the specimens vs. a suitable reference electrode in an electrolyte which serves as a mild corrodant for the exposed basis metal. The corrosion potentials of gold‐plated copper specimens in 0.1MNH4normalCl electrolyte are shown to vary with the exposed area fraction of copper according to an expression derived by Stern. It is possible to calibrate the technique so that values of the exposed basis metal area fraction in electroplated specimens can be estimated to a reasonable approximation. The method is simple and offers very high sensitivity, particularly at low porosities. Operational considerations and sources of error are discussed.

mentioning

confidence: 99%

Electrolytic Determination of Porosity in Gold Electroplates

Morrissey¹

1970

“…This work was motivated not so much by the ohmic and kinetic limitation at short times but more by the shape of the logarithmic current-time curves obtained in the measurement of integral diffusion coefficients (5), the study of the effect of ionic migration on limiting currents (6), and attempts to obtain limiting currents in cupric sulfate solutions in the absence of sulfuric acid (7). Under certain conditions, the current overshoots the limiting current.…”

Section: Discussionmentioning

confidence: 99%

A Rapid Anodic Porosity Test for Ni-Fe Electrodeposits on Copper Wire

Freitag¹

1970

A 10‐min semiquantitative polarographic test is described which measures the area of copper substrate left exposed by pinholes or defects in electrodeposited memory wire. The wire sample is made the anode in an electrolytic cell, the Ni‐Fe outer film is rendered passive with a controlled potential sequence, and the anodic current due to oxidation of exposed copper is recorded as a function of potential. The height of a copper passivation peak is measured, and this height is shown to be proportional to exposed Cu area. The method is useful in quality control and in following the course of corrosion in environments when the attack at local defects is the major mechanism.

“…Leakage Current Methods Leakage current measurements were first applied to the determination of porosity in electrodeposits of nickel and cobalt on steel by Shome and Evans (10). Their procedure was to measure the cell current passed when the specimens were connected, in an electrolyte of 3% NaC1 ~ 0.1% Rochelle salt, to a large copper gauze which served as an auxiliary cathode.…”

Section: Linear Polarization Methodsmentioning

confidence: 99%

Electrolytic Determination of Porosity in Gold Electroplates

Morrissey¹

1972

Anodic polarization curves of gold and gold‐plated copper specimens have been obtained at a sweep rate of 10 mV/min in 0.1MNH4normalCl electrolyte. The curves obtained are found to be linear over ranges of potential approaching 50 mV displacement from the free corrosion potential. From the data obtained, values of the free corrosion potential, the polarization admittance, and the leakage current are extracted and compared for each specimen. Agreement between the corrosion potential and polarization admittance values is excellent. It is shown that the polarization admittances of gold‐plated copper specimens in 0.1MNH4normalCl vary with the apparent exposed area fraction of copper according to expressions derived by Stern. Agreement between the corrosion potential and leakage current values is fair, becoming poorer as the polarizing potential is displaced farther from the free corrosion potential. It is shown that at a given value of the polarizing potential, leakage currents passed by gold‐plated copper specimens in 0.1MNH4normalCl vary directly with the apparent exposed copper area. Anodic current densities and minimum limits of detectability for the various techniques are discussed.