Observation of tunnels formed on D. C. etched {100} highly ordered aluminum and analysis of the tunnel shape near the tunnel mouth were performed by using the oxide replica method. The tunnel shape near the tunnel mouth was measured as a function of the tunnel depth (l_i) for the tunnels obtained by the D. C. etching in HCl, NaCl, AlCl₃, HCl+AlCl₃, NaCl+AlCl₃, H₂SO₄+AlCl₃, and HCl+NaCl aqueous solutions. The tunnel width (Wi) tapered exponentially with l_i, i. e., log (W_i/W_o)=a·l_i, where W_o is the tunnel width at the tunnel mouth, in all the solutions examined in this study. In the solutions containing H⁺ ions, the tunnel width increased with the increase in the tunnel depth near the tunnel mouth at depths of 4 to 5μm from the aluminum surface, followed by a decrease of the tunnel width at depths of 5μm or more. The degree of expansion of the tunnel width increased with increasing H⁺ concentration. This indicated that the increase of the tunnel width with an increasing tunnel depth near the tunnel mouth was closely related to the presence of H⁺ ions. Corrosion (Al→Al³⁺+3e^-, 2H⁺+2e^-→H₂) of aluminum near the tunnel mouth, in which H⁺ took part, was suggested as the origin of the tunnel width expansion near the tunnel mouth. In HCl+AlCl₃, NaCl+AlCl₃, and H₂SO₄+AlCl₃ aqueous solutions, the degree of expansion of tunnel width decreased rapidly compared to the HCl and AlCl₃ solutions. Al³⁺, Cl^-, and H⁺ ion played an important part in determination of the tunnel shape near the tunnel mouth. The rapid decrease of the degree of the tunnel width expansion near the tunnel mouth was considered to be caused by the increase in the concentration of Al³⁺, Cl^-, and H⁺ ion in the tunnel, followed by the hindrance of the electrolytic dissolution of Al.

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Resistometry has been applied to the corrosion studies of Fe, Ti and Al electrodes in a thin wire form. Dissolution depth of Fe wire in the active potential range during potential sweep was estimated from resistance data and was consistent with the value obtained from the electric charge. In the passive potential range, the dependence of resistance on growth of the passive film and change in space charge layer of the passive film were observed. For Ti and Al electrodes, resistance changes due to anodic oxide growth were observed. In the high voltage range, however, the temperature of specimens rose due to increase in electric energy loss in the oxide film, and thus the resistivity increased apparently. For Ti electrodes, the growth of the hydride layer was monitored using resistometry under the condition of electrochemical hydrogen loading. For Al electrodes, cathodic dissolution under the condition of hydrogen evolution was measured. In the acidic solution, cathodic passivation phenomenon was observed in which a deposition layer of Al hydroxide suppressed the cathodic reaction.

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Nickel and oil-containing microcapsule composite coatings were fabricated. The oil-containing microcapsules were synthesized by the interfacial polymerization of the oil-soluble and water-soluble monomers. The influences of the intension substance and the surfactant on the size distribution were discussed. The surface and the cross-section of the oil-containing microcapsules composite coatings were observed by scanning electron microscope. From the result of the observation, it was found that microcapsules were involved in the nickel matrix. Furthermore, a new composite plating method, in which the 100% of the microcapsules in the electrolyte solution were incorporated into the nickel matrix, was developed. In addition, the stability of microcapsules in the nickel matrix was investigated. It was confirmed that microcapsules in the nickel matrix were stable.

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Aluminum specimens were covered with SiO₂ film by a sol-gel coating and then anodized galvanostatically in a boric acid solution. Time variations in the anode potential during anodizing were monitored, and the structure and dielectric properties of anodic oxide films were examined by TEM-EDX, and electrochemical impedance measurements. It was found that anodizing of aluminum coated with SiO₂ films leads to the formation of anodic oxide films that consist of an outer Al-Si composite oxide layer and an inner Al₂O₃ layer at the interface between the SiO₂ film and the metal substrate. The breakdown potential of anodic oxide films formed on specimens with SiO₂-coating was about 100 V higher than that without SiO₂ coating. The capacitance of specimens after sol-gel coating and anodizing was slightly higher than that without sol-gel coating. In the film formation mechanism, the conversion of Al₂O₃ into Al-Si composite oxide at the interface between the inner and outer layers is discussed in terms of inward transport of Si-bearing anions across the outer layer.

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The effects of surface morphology of zinc electroplated steel sheet on high power YAG laser lap weldability were studied. In zero gap lap welding, clearance was naturally formed in uneven zinc electroplating that controlled the surface morphology, and suppression of sputtering was made possible by the clearance. It was found that the laser lap weldability was improved by the uneven zinc electroplating.

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