On the surface of graphite suspended in acidic solution, graphite-oxygen species are formed by anodic oxidation or by bubbling of ozonous air. These graphite-oxygen species on the surface of graphite are stable in the suspension solution and have a noble redox suspension potential. Based on this special character of graphite, the graphite-suspension which has such high oxidation ability could be applied to the etching of copper. The etching takes place only at the contact part with graphite, and then a troublesome undercut in etching can be prevented by controlling a size of graphite particles. The etching velocity of copper increases with increasing the amount of graphite and with diminishing in size of graphite, since the etching velocity depended mainly on the total surface area of suspended graphite particles at the same suspension potential. Then, the flow rate of suspension solution was increased in order to increase the etching velocity, but the increasing degree of etching velocity was limited by the reduction rate of oxygen species on graphite. The reduction rate depends upon the kind of graphite, and the ability can be experimentally evaluated by the cyclic voltammetry. The dissolved copper by this etching method can be easily recovered at cathode simply by an electrolysis of the solution without graphite particles.

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The properties of anodic coatings on high strength and free cutting aluminum are often not adequate for their intended uses, due to Cu, Pb and Bi in the aluminum alloys. In this study aluminum alloys, 2014, 2017, 2024 and KS21 were anodized with an alternating current to investigate the characteristics of the anodic coatings. It was found that the hardness of the coatings increased with decreasing temperature and electrolyte concentration. At temperatures below 15°C, the hardest and most uniform coatings were obtained with 35% sulfuric acid bath. The surface roughness of coatings formed with the alternating currents was smaller than that obtained with direct currents. The bath voltages for alternating currents were lower than those for direct currents. The addition of oxalic acid to sulfuric acid baths improves the coating properties, the improvement is remarkable when the concentration of oxalic acid is higher than 20g/l. Both hardness and thickness of the coatings on free cutting alloys were lower than those on high strength alloys, and this may be attributed to Cu, Pb and Bi.

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The selective removal of trace copper (II) ion in Watts nickel bath was studied by using chelating reagents, 2-quinolinecarboxylic acid (QA), N-nitroso-N-phenylazanol ammonium salt (CP), 2-mercapto-benzothiazole (MBT), and (2-hydroxylphenylmethylene) azanole (SA). These chelating reagents formed insoluble complexes with copper (II) ion in the bath. Residual copper (II) ion lower than 0.1mg/l was attaind by the addition of MBT or SA, whereas the residual ion was below 5mg/l for QA or CP. Since the chelating reagents have harmful effects on the appearance of nickel deposits, the bath had to be treated with activated carbon prior to use. Amounts of activated carbon, required for reducing the concentration of chelating reagents from 100mg/l to harmless value, 10mg/l, were 0.7, 1.4, 3.0 and 4.0g/l for MBT, SA, QA and CP respectively. Activated carbon modified with the chelating reagent was also useful for the selective removal of copper (II) ion. Additional activated carbon treatment was not necessary, because the desorption of SA from the modified activated carbon into Watts bath was too little to be harmful.

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The behavior of butynediol used as a brightner in nickel plating baths was studied measuring the concentration change of butynediol in the baths with plating time, and the carbon contents in nickel deposits. Butynediol was decomposed electrochemically to butanediol on the cathode surface at a definite rate controlled by diffusion controll of butynediol, and the most part of butanediol, the reaction products, accumulated in the plating solution not in the nickel deposits. Therefore, the decrease of current efficiency in bright nickel plating was considered to be caused by the reductive reaction of butynediol. Butynediol, the addition agent, which was electrochemically reduced on the electrode surface under the condition of diffusion controll behaved as a leveller.

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Changes in the cathodic overpotential, differential capacity, and morphology of the silver deposits were examined as a function of the current modulation in the pulsed current electrolysis in silver cyanide and silver-ammonia complex baths. Finer grained silver deposits were obtained by increasing pulse current density and pulse on-time or by decreasing off-time. Under these conditions that give finer deposits, cathodic overpotential significantly increased independent of the plating bath, but the changes in the differential capacity and the orientation of the silver deposits differed in trends depending on the individual system. The factors affecting the surface morphology of the silver deposits in the pulsed current electrolysis were discussed in relation to the nucleation energy, concentration of the adions on the electrode surface, and adsorption of the species in the electrolyte.

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The morphology of pulse-electrodeposited tin from acid stannous sulfate baths with or without additives has been studied by means of scanning electron microscopy, X-ray diffraction, as well as throwing power and pinhole tests. The grain size of tin deposit was dependent on average current density, duty cycle and pulse time. At constant average current density and pulse time, the grain size decreased with decreasing duty cycles. Furthermore, the grain size was reduced with increasing the pulse time at fixed average current density and duty cycle, mainly because of the increase of overpotential. When the electric charge per unit pulse exceeded 10mC. cm^-2, however, the deposit was of either needle or spot-type. The preferred orientation of tin deposit changed with increasing the average current density in the order of [100], [110], and [101], which coincides with Pangarov's theory. Pulse plating scarcely improves the throwing power compared with D. C. plating. Minimum thickness of pinhole-free deposit was reduced with decreasing the duty cycle.

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