The electrodeposition of Fe Ni alloys was performed galvanostatically in the sulfate solutions of pH 1 3 at 40°C and the alloy deposition behavior was compared with that of Zn iron group metal alloys to investigate their codeposition mechanism. The deposition behavior of Fe Ni alloy showed a typical feature of the anomalous codeposition, in which electrochemically less noble Fe deposits preferentially under most plating conditions. The anomalous codeposition behavior in Fe Ni alloy deposition was evidently dependent on the pH buffer capacity of the solutions. This can be explained in terms of the preferential adsorption of FeOH on the deposition sites of more noble Ni due to the extremely smaller dissociation constant of FeOH ＋ than NiOH ＋ in the multi step reduction process of hydrated iron group metal ions. Keywords: electrodeposition, iron nickel alloy, anomalous codeposition, iron group metal

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of Al and Al-Mg alloy was investigated by means of polarization curves in solutions containing 300 ppm of Cl À and by surface analysis. The potentials for pitting corrosion of Al and Al-Mg alloy were clearly shifted in the noble direction by the ECAP process, indicating that this process improves resistance to pitting corrosion. SEM observations revealed that pitting corrosion occurred near impurity precipitates and that the size of the impurity precipitated decreased as a result of the ECAP process. The time-dependence of corrosion potential and the polarization resistance determined using the AC impedance technique suggest that the ECAP process increases the rate of formation of Al oxide films. The improvement in pitting corrosion resistance of Al and AlMg alloy by ECAP appears to be attributable to a decrease in the size of impurity precipitates and an increase in the rate of formation of Al oxide films.

Zn electrodeposition was performed galvanostatically on steel sheets at 1 500 A/m 2 in an agitated sulfate solution at 40°C to investigate the effect of preadsorption of organic additives on the lightness and morphology of Zn. The organic additives employed were classified into two types: 1) polyethylene glycol (PEG), gelatin, and stearyl dimethylbenzyl ammonium chloride (SDBAC) (Type I), which exhibit a polarization effect for Zn deposition; and 2) saccharin and sodium lauryl sulfate (Type II), which exhibit no polarization effect for Zn deposition. The platelet crystals of deposited Zn were reduced in size with preadsorption of all the organic additives considered. The observed decrease in the size of Zn platelet crystals with preadsorption is attributed to both an increase in the overpotential for Zn deposition and a decrease in the epitaxial growth of Zn on steel substrates. The preferred orientation of the {0001} Zn basal plane significantly decreased because of an increase in Zn deposition overpotential owing to preadsorption of PEG and gelatin, and the orientation slightly decreased with saccharin and sodium lauryl sulfate in spite of the absence of a polarization effect on Zn deposition. The surface roughness of deposited Zn decreased with preadsorption of organic additives with the exception of SDBAC. This is due to a decrease in the size of Zn platelet crystals. The lightness of deposited Zn was increased by preadsorption of organic additives with the exception of SDBAC. Because Zn deposited nonuniformly with preadsorption of SDBAC, the surface roughness of Zn increased and the lightness decreased.

The effect of equal channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al and Al Mg alloy was investigated by electrochemical techniques in a solution containing 0.25 mol/L of AlCl 3 and by surface analysis. The time required before initiating pitting corrosion of anodized Al was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. However, in anodized Al Mg alloy, the pitting corrosion occurred earlier with ECAP than without, showing that the corrosion resistance was worse with ECAP than without. SEM and EPMA observation revealed that pitting corrosion of anodized Al occurred around the impurity precipitates and that the size of the impurity precipitate decreased as a result of the ECAP. The improvement in pitting corrosion resistance of anodized Al by ECAP appears to be attributable to a decrease in the size of impurity precipitates. On the other hand, in anodized Al Mg alloy, cracks occurred in the anodic oxide films during initial corrosion and the cracks were larger with ECAP than without. It is assumed that the pitting corrosion was promoted by the cracks resulted from ECAP.