The corrosion resistance of Zn-Co-Mo electrogalvanized steel has been investigated, and the effect of Co and Mo in the deposit on the corrosion behavior has been discussed. 1) Zn-Co-Mo plated steel shows about 4 to 6 times better corrosion resistance than Zn plated steel in respect to the formation of red rusting by salt spray test, and the excellent resistance against the deterioration of PVC adhesion was observed under the salt spray test or immersion test (1% HF, 1% H₂SO₄, 5% NaOH or running water). 2) During the salt spray test, the corrosion potential of Zn-Co-Mo plated steel shifted slowly to the Fe potential. On the other hand, the corrosion potential of the Zn plated steel moves rapidly to the Fe potential. Though the initial corrosion current of Zn-Co-Mo plated steel is larger than that of Zn plated steel, the corrosion current of Zn-Co-Mo plated steel seemed to decrease with the corrosion progress, and it becomes smaller than that of Zn plated steel after all. 3) The cathodic reaction on the Fe surface exposed by the dissolution of Zn and the anodic reaction of Zn seemed to be suppressed by the corrosion products containing the Co and Mo compounds in the deposit, so that the corrosion resistance of Zn-Co-Mo plated steel was found to be superior to that of Zn plated steel.

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A bench scale experiment was conducted to clarify relations between the salt film (S.F.) treatment conditions and the descaling of stainless steels. The results are summarized as follows: (1) An aqueous solution of Na₂CO₃-NaNO₃-NaOH system was suitable for the cooling type S.F. treatment, because the solution was applicable to a variety of steels and at a wide temperature range. (2) For the temperature raising type, it was necesssry to use a heating furnace with an atmosphere containing little carbon dioxide to protect alkali hydroxide from carbonation, and the descaling was liable to be nonuniform. (3) Spraying of the S.F. solution through air jet type nozzles gave relatively good results, but there were still many problems to be solved.

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Electropolished 99.99% Al foil coupons were. galvanostatically anodized in C₂H₂O₄ solutions by applying a fixed amount of charge (7.2 Coulombs/m²). The morphology of the formed oxide (cell size, 2R, pore diameter, 2r, and barrier layer thickness, δ_b) was examined as functions of the acid concentration (2-8%), temperature (10-40°C) and current density (1-180Am^-2), by using electronmicroscopy and electrochemical techniques developed in a previous investigation. The morphology of the oxide films is solely the function of the anodizing voltage, E_a, while E_a is affected by the solution concentration, temperature and anodizing c.d. The density of oxide, ρ, is estimated to be 3.0-3.5, as being the weight of film divided by the volume of oxide. The value of ρ was found to increase with decreasing c.d. and increasing temperature and solution concentration.

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Bright zinc plating, from weak acidic (pH 5.5) chloride bath containing ZnCl₂, KCl and H₃BO₃ as main components, were investgated by Hull cell testings, scanning electron microscopic observations and cathodic polarization measurements. It was found that the addition of nonionic surfactant (nonyl phenyl eicosa-ethylene glycol ether: NPEGE), benzal acetone (BA), cinnamic acid (CA), 1, 2, 3-benzotriazole (BT) and nicotinic acid (NA) to the bath produced bright deposits under wide current density range. The range of the current density giving bright deposits widened with increasing zinc ion concentration. In all cases, however, bright deposits could never be obtained at current density higher than the limiting current. BA was an excellent brightener, but water-insoluble alone. NPEGE mainly severed as solubilizer for BA and CA. CA improved the appearance of the deposits at low current density and BT did so at lower current density region. NA improved the appearance of the deposits at high current density near or a little above the limiting current. SEM observations showed that the grain size from additive-free bath decreased with increasing the current density, but at higher than the limiting current. some of the deposits grew into dendrites. The bright deposits from additive bath had fine round grains, of which size ranged from 200Å to 600Å, and semi-bright deposits were needle-like crystals. Among the additives, NA behaved as a deepolarizer, but the others acted as cathodic polarizer, especially BA polarized severely.

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