Co-Mo alloy plating from ammonium-citrate bath was studied for the purpose of developing a new pretreatment method for direct-on enameling on steel sheet.
The effect of plating conditions on the Co/Mo alloy ratio was studied first, and on the basis of the results, the effect of the Co/Mo ratio on adhesion for direct-on enameling was examined.
It was found that: 1) Co/Mo alloy ratio in the electrodeposit was affected by bath composition including the concentration ratio of CoSO₄ to Na-citrate, the ammonium hydroxide concentration and pH. 2) To obtain excellent adhesion for direct-on enameling, Co-Mo alloy deposits on steel sheet should have Co/Mo ratio of less than 1.4:1 and coating weight of more than 1.5g/m² for both Co and Mo.

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The wear-resistance of Fe-1.5% Cu-0.6% C and Fe-2.0% Cu sintered ferrous products surface treated with bonding and carburizing was investigated. Low carbon (0.07% C) steel and cemented carbide alloy were used as rotory test pieces in the wear test. The surface of the bonded products was found to have higher wear-resistance than that of carburized products under the following sliding wear conditions: Fe-1.5% Cu-0.6% C or Fe-2.0% Cu-low carbon steel, lubricated; and Fe-1.5% Cu-0.6% C-low carbon steel and Fe-2.0% Cu-cemented carbide alloy, unlubricated. Oxidation or adhesion of frictional surface with rotory test pieces was less for the bonded products than for those that had been carburized. In the wear mechanism at slow sliding velocities under unlubricated conditions for bonded Fe-1.5% Cu-0.6% C-low carbon steel, oxidative wear was observed, and with increasing sliding velocity, there was a change from oxidative wear to mechanical wear. In the wear mechanism at sliding velocities between 0.1 and 4.4m/s under unlubricated conditions for bonded Fe-1.5% Cu-0.6% C or Fe-2.0% Cu-cemented carbide alloy, oxidative wear was mainly observed.

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Aluninum was anodized for different durations in a 13M H₂SO₄ solution (20°C) at constant voltages of 30, 35, 40, and 45V. It was possible to deposit nickel uniformly into the pores of the formed oxide without pre-treatment. Electrodeposition did not take place with films formed in dilute H₂SO₄ solutions. The behavior and mechanism of the elecctrodeposition were examined in relation to the film structure and the results are summarized as follows: Film structure-Reanodizing behavior of the specimens in a neutral borate solution suggests that the 13M sulfuric acid films have numerous micro voids in the barrier layer, probably penetrating through the oxide to the substrate metal, and formed as a result of the incorporation of SO₄^2- ions in the oxide and their partial removal during washing of the film with water. Deposition behavior-Electrodeposition was made in two steps in a solution of 70g dm^-3 NiSO₄⋅7H₂O-30g dm^-3H₃BO₃ (20°C), by first applying a small cathodic current of 0.05A·dm^-2 for 15min followed by 1.45A·dm^-2 for 45min. The first step was essential to form nickel nuclei in the micro voids, and a uniform deposit could only be obtained by the two-step procedure. The maximum thickness of the uniform deposit was found to increase with the voltage at which film was formed. The distribution of nickel in the pores and surface of the films was confirmed by XMA.

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Porous anodic oxide films formed on Al in an oxalic acid solution were hydrated in water at 99.5°C with and without additions of chromate, phosphate or nickel acetate. The hydrated films were then dissolved in a chromic acid-phosphoric acid solution. The changes in film structure during the hydration and dissolution experiments were followed by gravimetry and by impedance measurements in a neutral borate solution.
(1) As in pure hot water, pores of the film were filled up (or sealed) with hydrous oxide in a short time in waters containing chromate and nickel acetate, although slight dissolution of the film was observed. The water with phosphate did not hydrate the film but dissolved it to some extent.
(2) In the chromic acid-phosphoric acid solution, films hydrated in chromate-containing hot water dissolved faster and films hydrated in hot water containing nickel acetate dissolved slower than those hydrated in pure hot water. For all films, the dissolution rate was controlled by the dissolution of hydrous oxide which fills up the pores. The dissolution rate in general decreased with increasing electric resistance of the hydrous oxide.
The significance of the three existing methods of verifying the degree of “sealing”, the coloring method, the impedance measuring method and the acid dissolution method, is discussed.

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Silver-palladium alloy deposition from alkaline solutions containing EDTA, ammonium carbonate, and ammonia water has been studied. The cathodic potential for alloy deposition was -0.37V (vs. SCE) which was between those of Ag⁺ and Pd²⁺ single ion solutions. It was found that the silver deposition became the condition of diffusion controll, when palladium was deposited. This deposition of silver-palladium alloy was an anomalous codeposition, and the palladium content of electrodeposited alloy was always smaller than that of the electrolyte. The amount of palladium codeposited tended to increase with an increased in bath pH or current density, and decreased with an increase in bath temperature. Cathode current efficiency was about 70% irrespective of bath temperature. It improved with an increase in pH, and tended to decrease with higher current density.The electrodeposit of silver-palladium alloy had a crystal structure with no remarkable orientation. SEM photographs showed good adhesion and a smooth surface with no cracks.

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