Polarization behavior of tin anodes in H₂SO₄ of various concentrations and stannous sulfate plating baths was investigated by potentiostatic method.
The anodes with various lead contents were prepared by a conventional melting process.
The results obtained were as follows:
(1) An oxide film was formed on the surface of tin anodes at potentials above passivation. The film was stable at potentials up to -0.4V(vs. S.C.E.), but it was dissolved when the potential was lowered to the spontaneous electrode potential of tin.
(2) The polarization for tin anodes depended upon the concentration of H₂SO₄, which made the passivity prominent at 3N.
(3) The effect of passivity increased with the decrease in purity of anode and lead was the most toxic among impurities.
(4) Organic addition agents to the plating bath inhibited the anodic dissolution.
(5) It was found that the measurement of anode potential-current density curve was used for selecting an excellent anode for each of various plating baths.

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Ammonium hydroxide solution (2.3mol) containing ammonium tartrate (0.1mol), ammonium carbonate (0.1mol), and ammonium fluoride (0.27M mol) was used as an electrolyte for anodizing aluminum in alkaline solution.
A thick film (about 15μ) was formed on an aluminum specimen by electrolysis for 30min. under current density of 2Amp/dm² in this solution.
It was found by chemical analysis that the film contained about 1.2% of F^- and its density (10μ:1.8mg/cm²) was lower than that of the anodized film in H₂SO₄ (10μ:2.1mg/cm²). It had a high corrosion resistance to acid (H₂SO₄ 10%) and base (NaOH 10%), but its hardness was not so high.
It was supposed by electron microscopic examination of the surface and cross-section that the film had larger pores and cells as compared with the anodized film in H₂SO₄.
The double anodized film, which had been anodized in sulfuric acid after the electrolysis in alkaline solution, had higher corrosion resistance as compared with a double anodized film, which had been electrolyzed in reverse order. It was clearly observed by microscopy that the layer of 2ry oxide film was formed beneath that of 1ry oxide film.

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This study was made of the effects of saccharin sodium, p-toluene sulfonamide (hereinafter referred to as “PTS”), naphthalene 1.3.6-trisulfonic acid trisodium salt (hereinafter referred to as “NTS”) as stress-reducing agents on the bath composed of ferrous sulfamate, ammonium bifluoride, and sulfamic acid.
The addition of saccharin sodium to the acid sulfamate bath had a striking stress-reducing effect. A rapid decrease of stress was observed up to 0.2g/l of concentration of saccharin sodium, and the rate of decrease was less rapid up to 0.3g/l of the concentration. Finally, the stress tended to reach a constant value. The surface of the deposit from the bath containing 0.2g/l of saccharin sodium was not different from that from the bath containing no saccharin sodium; but the deposit from the bath containing 0.5g/l of saccharin sodium had a blackish gray surface.
The stress was reduced with the increase in concentration of PTS. However, it was increased with the increase in concentration of NTS from 10 to 20g/l, and then was reduced with the further increase of its concentration to 40g/l.

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For the estimation of corrosion resistance of composite platings, including a cobalt layer, the changes of the following factors with the progress of time were determined. The specimens used were cobalt from double salt type bath, copper from sulfate bath, and bright nickel. The tests were made on the following factors.
(a) Spoutaneous electrode potential of each specimen in CASS solution.
(b) Mixed potential of a combined specimen in CASS solution.
(c) Electromotive force between any two specimens in various accelerated corrosion solutions or in natural water.
The following conclusions were drawn from the consideration of experimental results.
(1) The Plating order for the most Suitable was as follows: Cu at fast, Co the next, and bright Nickel at last. The order of the Potentials was as follows:
Cobalt was least noble, Copper was the next, and bright nickel was noblest
(2) In chloride rich surroundings, the electromotive force between bright nickel and cobalt was larger than that detween any other specimens; therefore, copper layer was protected by cobalt layer.
(3) In chloride poor surroundings, copper layer was also protected by cobalt layer since copper layer was the noblest in these surroundings.
(4) By reasons of the above facts, the composite plating including a cobalt layer was suitable for preparing articles used in various different surroundings.

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The electrode potentials of pure iron covered with Fe₃O₄ film in acidic chromate solutions were measured at 25°C in relation to the Pourbaix diagram of Fe-CrO₃-H₂O system.
The potential at the early stage of immersion showed a stable value corresponding to the oxidizing reaction from Fe₃O₄ to γ-Fe₂O₃. The relation between the potential and pH value of the solution changed with the structural change of chromic ion species: Cr³⁺_ag. (pH<2), CrO^-_2aq. (2<pH<4), and CrO^3-_3aq. (4<pH).
The potential at about 30min. after immersion showed a stable value corresponding to the dissolution of iron. The relation between the potential and pH value changed with the structurall change of ferric and chromic ion species: Fe³⁺_aq., Cr³⁺_aq. (pH<2); FeOH²⁺_aq., CrO^-_2aq. (2<pH<4); and. Fe(OH)⁺_2aq., CrO^3-_3aq. (4<pH).
The observed pH-potential relations were discussed in connection with the electrochemical equilibrium of cathodic and anodic reactions on the surfaces. The electrode potential of the reaction of pure iron with chromic acid solution through the Fe₃O₄ film was found to have a correlation with the anodic reaction of solid electrolyte, i.e., the dissolution of Fe²⁺ from iron crystal surface into the Fe₃O₄ film.

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When the chromium diffusion coating of nickel superalloys was treated in a system containing iron, an extremely corrosive layer was often obtained and the chromium content of the layer was decreased.
This paper describes the chemical reactions on the metal surface and some experiments conducted for explaining the above phenomenon.
The results showed that the behavior of iron had bad effects on the properties of the diffusion layer such as decrease in surface chromium concentration, corrosion resistance, and oxidation resistance, acceleration in peeling of diffused layer and deterioration of diffusion agent.
Therefore, it was concluded that the mixing of iron with the diffusion agent must be prevented and the use of a mild steel vessel must be avoided.

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