Hisaaki Fukushima

Electrodeposition behaviour of zinc-iron group metal alloys from a methanol bath

Electrodeposition of zinc–iron-group metal alloys is carried out in a methanol bath. The effects of different parameters, such as bath composition and current density on current efficiency and alloy composition are investigated. Partial polarization curves of zinc and nickel are measured for both alloy and single metal deposition to evaluate the codeposition behaviour of zinc–iron-group metal alloys. Attempts are also made to confirm the proposed hydroxide suppression mechanism explaining the anomalous type of codeposition of zinc–iron-group metal alloys by investigating the role of water in the electroreduction process of zinc and iron-group metal ions.

Effect of electrolysis factors on crystal orientation and morphology of electrodeposited cobalt

AbstractCobalt electrodeposition was carried out using sulfate and chloride baths to investigate the effects of electrolysis factors on the crystal orientation and morphology of the deposits. The preferred orientation of Co deposited from the sulfate baths changed from (0 0 0 2) to (1 1

Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

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Mechanism of anomalous type electrodeposition of Fe-Ni alloys from sulfate solutions

0) plane with an increase in the deposition overpotential and the deposits showed the largest grain size with a smooth surface in the low overpotential region. On the other hand, no dependence of crystal orientation and morphology on deposition overpotential was found in chloride baths.

Effect of Equal-Channel Angular Pressing on the Pitting Corrosion Resistance of Al Alloy

The role of polyethylene glycol (PEG) as an additive in the electrodeposition of zinc–chromium alloys was investigated in sulfate baths containing trivalent chromium. PEG with high molecular weight enabled the codeposition of metallic chromium with zinc, while chromium(III) was present in the deposits obtained from the baths containing PEG with lower molecular weight as well as the PEG-free bath. The polarization curves for the alloy deposition revealed that PEG with high molecular weight polarized the deposition potential of zinc to the reduction potential of chromium to permit the codeposition of chromium with zinc.

Effect of Equal Channel Angular Pressing on the Pitting Corrosion Resistance on the Aluminum Alloys with/without Anodization

Abstract The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl 3 and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m 2 in a solution containing 1.53 mol/L H 2 SO 4 and 0.018 5 mol/L Al 2 (SO 4 ) 3 ·16H 2 O at 20 °C. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.

Effect of organic additives on the hardness of ni electrodeposited from sulfamate and watt's solutions

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- and by surface analysis. The potentials for pitting corrosion of Al and Al-Mg alloy were evidently shifted to the noble direction by ECAP process, indicating that this process improves resistance to pitting corrosion. SEM observation revealed that the pitting corrosion occurred near the impurity precipitates and the size of impurity precipitated decreased with ECAP process. The time-dependence of corrosion potential and the polarization resistance determined by AC impedance technique suggested that the formation rate of Al oxide films was increased with ECAP process. The improvement in pitting corrosion resistance of Al and Al-Mg by ECAP seems to be attributable to the decrease in the size of impurity precipitates and the increase in the formation rate of Al oxide films.

Characteristics of Iron-Group Metals in Simultaneous Deposition with Different Metal.

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 þ than NiOH þ in the multi-step reduction process of hydrated iron-group metal ions.