Polarization characteristics were investigated for electroless copper plating baths consisting of copper sulfate, EDTA, formaldehyde, glycine, potassium hexacyanoferrate (II) and triethanolamine. The effects of bath composition and convection on the electrode processes-oxidation of formaldehyde, deposition of copper and anodic dissolution of copper-were evaluated using a rotating copper disk as the working electrode. It was inferred that the rate of oxidation of formaldehyde was proportional to the amount of formaldehyde adsorbed in accord with the Langmuir isotherm. It was further suggested that hexacyanoferrate (II) was adsorbed in accord with the Langmuir isotherm for dissociation adsorption (n=2), retarding the above electrode processes. The effect of electrode rotation was significant only at high current densities where the diffusion of copper complex from/to the electrode was rate-determinating, while no substantial effect was found on local processes near the rest potential.
Fe-W alloy films were prepared by electrodeposition. Both amorphous and crystalline structure can be formed by controlling electrodeposition conditions. The effects of bath temperature and current density on their amorphization were investigated. Films with W content beyond a certain critical value WL were amorphous in structure, and the value of WL was affected by both bath temperature and current density. The Fe-W crystalline films prepared by electrodeposition were found to be substitutional solid solutions. The Fe-W amorphous films were subjected to annealing and DTA analysis, and information about amorphous structures and their energy states were obtained. A mechanism for the amorphization of Fe-W alloy films by electrodeposition is suggested based on the experimental results obtained.
The AC etching process of aluminum in HCl solutions was examined by capacitance measurement and galvano-dynamic voltammetry. It was found that the electrostatic capacitance of the etched specimens showed a maximum depending on the electrolytic conditions such as current density and frequency. The phenomenon is explained in terms of the change in the distribution of cubic pits reflected by the change of the protective behavior of the films formed on the pits surface in the etching. Scanning electron microscope examination of the films stripped from etched specimen revealed that they replicate the cubic pit propagation in the metal and that they have a duplex structure consisting of an inner anodic film formed during the anodic cycles and an outer film of hydrous oxide (the etch film), precipitated during the cathodic cycles. The anodic film next to the metal is thin and compact, while the etch film is thicker and shows granular structure. Film thicknesses for etching with 3.6%HCl solution (303K) at 0.3A/cm2 and 5Hz were about 4nm for the anodic film and about 16nm for the etch film determined using electron microscope by transmission of ultramicrotomed sectional specimens. It is concluded that whether or not the porous layer develops deeply into the metal by the etching depends upon largely the formation and local breakdown behavior of an anodic film covering the cubic pits at the propagation tips.
The AC electrolytic blue coloring of anodic oxide films on aluminum was studied in aluminum sulfate solutions containing nickel (II) sulfate, cobalt (II) sulfate or zinc sulfate. Electrolytes containing zinc sulfate yielded light grayish films, while those containing nickel (II) sulfate or cobalt (II) sulfate yielded gray, grayish blue, or blue colored films at voltages higher than 26V AC. Anodic stripping was conducted to clarify the mechanism of such color changes. The results suggested that Ni2+ and Co2+ were first reduced and deposited in the film pores and that the deposits were than hydroxidized and oxidized by OH- produced by the electrolysis of the water. It is also concluded that the aluminum hydrate and oxide on the upper sides of the films were formed simultaneously by migration and deposition of multinuclear complex ions of Al3+.
Silver, copper and steel specimens were exposed for 14 days in a laboratory at wind velocities of 0-3m/s and atmospheric pollutants were trapped on collecting devices. The corrosion products on the specimens were then analyzed by Auger electron spectroscopy. The collecting devices used and analytical methods applied for the various pollutants were as follows: 1) SO2: PbO2 cylinder and barium chromate-diphenylcarbazide absorptiometry 2) Cl- in solid compounds: Dry gauze and mercury (II) thiocyanate absorptiometry 3) Cl- in acidic gases: Alkaline K2CO3 filter paper and mercury (II) thiocyanate absorptiometry 4) NO2: Alkaline filter paper and naphthylethylenediamine absorptiometry 5) H2S: Zinc acetate filter paper and methylene blue absorptiometry. Increase in wind velocity enhanced the deposition rate of pollutants on the collecting device and accelerated the corrosion of metal specimens.