The cathodic current efficiency for chromium deposition from oxalic acid baths containing, chromic acid and ammonium sulphate, has been examined over a wide range of bath compositions and plating conditions. High current efficiencies were obtained in baths containing 100g/l total chromium, 48g/l hexavalent chromium, 75g/l (NH₄)₂SO₄. The current efficiency increased with decreasing current density and bath pH, and with increasing bath temperature. At the best current efficiencies, however, bright chromium deposits were not obtained, and to obtain bright chromium deposits, hexavalent chromium concentration should be 12-38g/l.

抄録全体を表示

Optimum bath compositions and plating conditions were experimentally sought for obtaining bright chromium deposits from CrCl₃⋅6H₂O-n-propanol baths containing cationic and anionic surfactants and the effects of addition of the surfactants on the cathode current efficiency were studied. The appearance of bright and adherent deposits was affected by plating time, bath temperature and applied current density. For promising chromium deposition, cationic and anionic surfactants had the effectiveness in the following order
(C₂H₅)₄NCl≈(C₂H₅)₄NBr≥n-C₁₂H₂₅ SO₃Na(DBS)≈n-C₁₅H₃₁COONa(SP).
Mirror bright deposits of chromium were obtained from the bath consisting of CrCl₃⋅6H₂O 100g/l and surfactants 5.0g/l at 15-25mA/cm², 30°C and 3-10min, plating time interval. The highest current efficiency of 50% was obtained in a chromium plating bath of CrCl₃⋅6H₂O 100g/l and DBS as the additive at 25mA/cm², 30°C and 3min, plating time interval. X-ray diffraction analysis showed that the preferred orientation of the Cr deposits was strong in (210) plane. In the case of the addition of (C₂H₅)₄ NCl and DBS the mean lattice constant and grain size of the deposits were found to be 4.57-4.58Å and ca. 85-100Å, respectively. The thickness of the deposit as plated was about 0.5-max. 3.6μm.

抄録全体を表示

Bulk plating of nickel from Watts bath has been studied using a box type vibratory barrel. Effects of cell current and vibrating condition on the electric contact between collector electrode and specimens, the spread of the deposit thickness and on the fluid state of specimens were investigated. The mixing rate of fluidized specimens increased with increasing frequency and amplitude of the cell. On and off-time for the electric contact between collector electrode and fluidized specimens were observed periodically the same to the vibration frequency of the cell. When the cell current and the amplitude are big, collector electrode tends to be passivated increasing individual difference in the deposit thickness. The spread of the deposit thickness could be contracted to about 3% in relative standard deviation under suitable conditions.

抄録全体を表示

The gas sulfunitriding of steel in CS₂ added atmospher was investigated. A test piece of S 45 C steel was treated in an atmospher of 50% NH₃ and 0.006% CS₂ added to propan converted carrier gas at temperature of 843K for 10.8ks. It was confirmed by X-ray diffraction that the surface products were Fe_1-xS, FeS, Fe₃N and Fe₄N respectively. The compound layer was observed on the cross sectional microstructure of treated specimen. The hardness gradualy increases toward the inner layer and reached maximum value. From those results the gas sulfunitriding of steel was possible used a CS₂ added atmospher.

抄録全体を表示

Electropolished 99.99% Al foil coupons were anodized in H₂SO₄ solutions of 0.5-4.0mol·dm^-3 at 10-40°C, by applying a constant current in a range of 0.5-50mA·cm^-2, Morphology of the oxide films was examined using electronmicroscopic and electrochemical techniques. For the accurate estimation of the number of pores, N, from electronmicrographs, the pores were widened by chemical dissolution of the oxide in a H₂SO₄ solution before the film was stripped from the substrate metal. The total film thickness, h, was estimated from the sections of films under a scanning electronmicroscope, and the pore radius, r, was calculated from the porosity of the oxide, α(=Nπr²), measured by the pore-filling method proposed by Middelhoek. The estimation of the barrier layer thickness, δ_b, was made according to Hunter's principle by measureing the voltage jump, E_j, when applying a small anodic current in a neutral borate solution. The thickness/voltage ratio, δ_b/E_j, was determined from the time-variations in the pore-wall thickness, δ_p, and E_j during chemical dissolution of the oxide, on an assumption that δ_b and δ_p thin at equal rates. In agreement with the results reported previously, N decreases and r and δ_b increase as the anodizing voltage, E_a, increases, but the results of this investigation clearly show that these quantities are solely the function of E_a although E_a is strongly affected by the solution condition and anodizing c.d. It is demonstrated that δ_b/E_a ratio is not constant but decreases with increasing E_a. For films formed with a fixed number of coulombs, the value of h somewhat increases with increasing E_a, solution concentration and temperature. The density of oxide ρ, is estimated to be 3.0-3.5 by dividing the weight of the film by the oxide volume calculated from the values of h, N, r and the chemical dissolution rate of the pore-wall during anodizing. It is interesting to note that ρ decreases with increasing E_a, solution concentration and temperature. The significance of the techniques of determining the quantities describing the film structure is discussed.

抄録全体を表示

The pulse wave was synthesized by chopping of the d. c. constant voltage source using a microcomputer and a power transistor. Anodic oxidation of aluminum was performed by these synthesized pulse wave. The current waveform of anodic oxidation was classified into three types according to the shape and the number of inflections: the type B by which a barrier layer was formed, the type P by which a porous film was formed and the type D by which the anode was dissolved. The current waveform, observed when anodic oxidation of aluminum was performed in a electrolyte of 0.05M borax added to 0.5M boric acid or of 9.08M phosphoric acid, was influenced by the temperature of the electrolyte and the anodizing time. It was evident that the barrier layer of the phosphoric acid film was chemically dissolved when the OFF time of the pulse wave was changed from 25ms to 50 ms. No capacity current at the start of anodic oxidation in 1M sulfuric acid was observed even when the current waveform for each pulse every 25ms was stored in a wave memory. The Al³⁺ ions in 1M sulfuric acid were found to cause a major disturbance in the leading edge of the capacity current. The similar phenomenon also appeared when stirring of the electrolyte was stopped.

抄録全体を表示