The effects of the cobalt and molybdenum additives on the structure of the Zn-Co-Mo layer electroplated on steel sheet were investigated by scanning electron microscopy, electron and X-ray diffraction. It was found that the plated layer was composed of bulk crystals rich in Co and micro crystals rich in Mo. As the amount of the deposit increased, bulk and micro crystals formed in several layers discontinously. The orientation of electroplated Zn deposits changed when Co and Mo were added. In the plated layers of Zn-Co-Mo, (00·2) and (10·3) decreased but (10·1) increased. The chemical state of Co and Mo in the plated layer could not be analyzed by X-ray diffraction or electron diffraction.

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Pure aluminum specimens were anodically oxidized in 13M and 1.5M sulfuric acid solutions at constant c. ds, and measurements were made of the amount of Al³⁺ ions accumulated in the formed oxide (W_f), the amount dissolved in the solution (W_d), and the coating ratio of the film. It was found that the sum of W_f and W_d was always equal to the total amount of oxidized aluminum (W_T) as calculated from the quantity of electricity. The amounts of W_f and W_d increased almost linearly with anodization time t_a. For any given value of W_T, the value of W_d obtained was smaller for the 13M solution than for the 1.5M solution, suggesting that the dissolution of the barrier layer at the pore-base proceeds more slowly in the 13M solution than in the 1.5M solution. This concept explains the high voltages and high current efficiencies observed for the formation of 13M films. Since the 13M films had smaller values of W_d and larger amounts of SO₄^2- ions compared to the 1.5M films, their weights and coating ratios were always larger. In the case of the 13M films, η and CR decrease appreciably with the lapse of anodizing time. This is due to the marked chemical dissolution of the pore walls during anodization.

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The effects of brighteners on zinc electroplating from alkaline zincate baths have been investigated by electrochemical methods, scanning electron microscopy and X-ray diffraction. Bright zinc electrodeposits obtained under diffusion-controlled zinc electroplating exhibited the preferred {1120} orientation parallel to the surface of the substrate. These results were interpreted in the light of deformation twinning on the basal plane, which caused the basal plane platelets to be aligned perpendicular to the substrate. Brightener was adsorbed on the electrode preferentially by shifting the impressed potential in the less noble direction. This resulted in strongly preferred {1120} oriented deposits at higher overpotential, and the range of bright electroplating extended even to electrolysis under diffusion-controlled zinc electroplating. It was also found that the overpotential for hydrogen evolution reaction on the zinc deposit with preferred {1120} orientation was smaller than that of other crystal facets of deposits. The strongly preferred {1120} oriented deposition caused the cathode potential to reduce the extent of polarization by accelerating the hydrogen evolution reaction. The Tafel slope of hydrogen evolution during zinc electroplating changed from 40 to 50mV/decade at lower overpotential to 130 to 140mV/decade at higher overpotential.

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The structural forms of interference colored films obtained by polarization in sodium hydroxide solution were characterized by scanning electron microscopy, and the value of corrosion resistance in the films was evaluated by pitting electrode potentials. The crystalloid structure of the films was similar to aggregations of short woolen yarns. The form of the film changed with increases in the amount of anodizing charge, from granular initially to a form similar to short woolen yarns. Film thickness increased lineary with increases in the amount of anodizing charge from 0.3 to 0.8C/cm². The corrosion resistance of the interference colored SUS 304 stainless steel was the same or higher than as that of passivated SUS 304 stainless steel.

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An attempt is made to explain steady voltage-log current (E_a-log i_a) curves obtained for the anodization of aluminum in acid solutions, by applying a theory so far reported for high-field ion conduction in crystalline solids. The theory is modified to some extent by taking into account two factors: the semi-spherical shell structure of the barrier layer by which the applied voltage is sustained, and the formation and repair of defects in the barrier layer which are appreciable at higher voltages. The interpreation of E_a-log i_a behavior, including the effect of temperature, is quite satisfactory.

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