The authors studied the effects of various sorts of amines and ammonium salts upon the formation bohmite film from ammonium base bath by chemical conversion. The results obtained were as follows. (1) Triethanolamine formed a stable chelate compound which accelerated the formation of bohmite film. (2) Ammonium carbonate had good effects upon the continuance of bath composition by the following reactions: 2Al+(NH₄₎₂CO₃+3H₂O→2NH₄AlO₂+CO₂+3H₂, 2NH₄AlO₂+H₂O→Al₂O₃+2NH₄OH, 2NH₄OH+CO₂→(NH₄₎₂CO₃+H₂O, (3) The ammonium hydroxide bath containing triethanolamine and ammonium carbonate continuously formed a very stable böhmite film on Aluminum and Aluminum alloys having no bad odor.

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For the purpose of studying the attack of hot dip galvanizing bath against the kettle and the coating machine, the authors made experiments on attack against various kinds of carbon steels (C: 0.02-0.2%) with molten zinc bath containing aluminum (0-0.3%) at 440-480°C. The results obtained were as follows: (1) In the zinc bath containing no aluminum, the attack on steels due to the reaction of Fe-Zn always conformed to the “Law of parabolic attack”. However, when aluminum was contained in the bath, the reaction of Fe-Zn passed the following three periods: Inhibition period→Acceleration period→Regular period (conforming to the “Law of parabolic attack”). (2) The duration of each of inhibition and accaleration periods was longer with the increase of aluminum content and the drop of bath temperature. (3) The reaction velocity for attack after reaching the regular period increased with the increase of aluminum content and the rise of bath temperature. (4) The iron loss constant in the reaction of regular period in the bath containing aluminum was expressed by the following formula: C=K[Al%]ⁿ: where C: Iron loss constant [(g/cm²⁾²/min.]×10^-8, n: Reaction index, K: Reaction coefficient, (Values of n and K varied according to the kind of steels and bath temperature). (5) The activation energy in the reaction of regular period (Q kcal/mol) for the bath containing aluminum was markedly greater than that for the bath containing no aluminum. In other words, the attack on steels with the bath containing aluminum was remarkably accelerated by a slight rise of temperature.

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The effects of sulfur contained in gas oil on high temperature oxidation of stainless steel was investigated by exposing the specimens to combustion gases containing various amounts of sulfur. The experiments were conducted in the temperature range of 850-1000°C for 20-120min. The weight increase of specimens by oxidation was remarkable with the increase in sulfur content of the gas oil up to 0.33%.; but the more increase of sulfur content had little effects. Sulfur was not detected in the oxidized surface layer by X-ray diffraction, the reason of which was theoretically discussed.

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The greasy layer remaining on aluminum as rolled is usually vaporized during annealing process; and contact angle is most commonly measured to check if the surface is free from the organic contaminations. In this paper, the possibility and limitations of applying ellipsometry for such a measurement were examined in the hope that the thickness of the greasy film might be determined more quantatively. Because of an complicated calculation of two-layer system consisting of both aluminum oxide film and the grease layer, an approximate method was used. The validity of this approximation was ascertained by measuring the built-up film of stearic acid on electropolished aluminum, the thickness of which had been previously known. The variation in the greasy layer thickness, thus measured with the specimens heated at variety of temperatures, indicates that the remaining oil on aluminum is almost completely depleted at temperatures higher than 400°C and then oxidation of aluminum takes palce instead.

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The electrodeposition mechanism of water soluble resins on the anode was investigated by measurements of analytical chemistry. At first, the deposition reaction of resins on anode was studied on the sheet steel for practice; and then, the amount of metal dissolved from the anode into the film was measured when phosphated galvanized sheet steel (which is usually used as the anode substance for electrodeposition) was used as anode. The results obtained were as follows. (1) The deposition reaction of water-soluble resins showed different results according to the kind of anode substances. (2) In most sheet steels except for galvanized sheet, the deposition of the resins on the anode was mainly due to the neutralization of carboxyl anions with protons formed by electrolysis of water. (3) In the galvanized sheet, the resinification reaction of carboxyl anions with zinc ions dissolved from the anode occurred concurrently with the reaction mentioned above. (2) In these experiments, nearly up to a half amount of carboxyl anions reacted with zinc ions for resinification. (4) When the phosphated galvanized sheet was used as anode, the ratio of dissolved zinc to the deposited film was constant independent of the time and temperature for electrodeposition; however, the ratio of phosphorus between the two decreased with the increase of time and the rise of temperature for deposition.

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This paper describes the electrodeposition of nickel from Ni(CF₃COO)₂-NH₄Cl-MeOH solutions for studying the electrodeposition mechanism of nickel. Bright and smooth nickel deposits were obtained from Ni(CF₃COO)₂ 500g/l-NH₄Cl20.0g/l-MeOH bath under current density of 2.0-22.0Amp/dm² at 30-50°C. The current efficiencies in this case were about 100% for both of cathode and anode. The rate controlling step of electrodeposition of nickel from Ni(CF₃COO)₂-NH₄Cl 20.0g/l-MeOH bath under current density of 1.0-5.8Amp/dm² was a charge transfer reaction. The main values in these experiments were as follows: Apparent transfer coefficient: α_c=0.75, Apparent valence: n=0.78, Apparent exchange current density: i_oc=0.23Amp/dm², Tafel slope: b_c=-0.12V, Apparent activation energy: E_c=5.7kcal/mol.

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The conditions for obtaining brass platings from non-cyanide bath of the composition mentioned below were studied with respect to polarization curve, analysis of deposited metal, measurement of current efficiency, visual test of deposits, etc. The bath was composed of 60-100g/l of NaOH, 5-20 ml/g of glycollic acid, and ZnO and CuSO₄. 5H₂O (concentration of total metal ions was less than 4g/l). Summary of test proceduse was as follows. When the polarization was beyond the threshold current density of each metal (about 5mA/cm²), a yellowish brass deposit of normal composition was obtained. However, when the current density was lower than that, only Cu was deposited. The current density was in the range of 80-30% in practice. The efficiency was promoted when the concentration of total metal ions was higher and the current density was lower. The zinc content of deposit was about 5% larger than that of bath composition. The addition of 0.5g/l of glatine gave better appearance of the deposit. When the deposited alloy was settled in the bath for a long period, its color was periodically changed as golden→magenta→blue→green. In conclusion, non-cyanide brass platings were obtained as above under almost the same conditions as in cyanide baths, except for that both of metal concentration and current density are not very high.

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