The composition of cathode films formed on tin in CrO₃ solutions with and without the addition of H₂SO₄ was examined by ESCA as a function of cathode potential. In general, films consist of an outer chromic chromate layer and an inner stannous-stannic oxide layer, and changes in the composition with potential are reflected by complex current-voltage curves consisting of several current waves. A metallic tin (Sn⁰) spectrum appeared at potentials below the natural potential, and the spectrum intensity ratio Sn⁰/(Sn²⁺+Sn⁴⁺), showed minima at the peak current potentials and maxima at the minimum current potentials. Chromic chromate films consisted mainly of trivalent chromium compounds. In the range more negative than about -0.6V, a hexavalent chromium compound was found in cathode films, and the oxide layer of tin consisted mainly of stannic oxide. Thus it is considered that changes in the chemical state of the tin electrode play an important role in chromium deposition.

抄録全体を表示

Relations between coating conditions and properties of the TiC layer formed on SUS 304 stainless steels by activated reactive evaporation (ARE) were studied at electron beam (EB) emission currents ranging from 0.15 to 0.25A, and acetylene gas pressures ranging from 5×10^-4 to 1×10^-3 Torr. Other parameters were fixed: ionization current substrate bias=-2kV, and substrate temperatrue=400°C.
Preferable coating condition differed depending on the properties required. (A) Measurement of coating rate and ionization rate showed that an EB emission current of more than 0.17 A was required at any acetylene pressure. (B) Mesurement of composition by EPMA, lattice constant by X-ray diffraction and micro-vickers hardness of the TiC layer showed that the lowest possible EB emission current and the highest possible acetylene pressure was preferable. (C) Observation of adhesion showed that the lowest possible EB emission current and the lowest possible acetylene pressure was preferable.
Based on these observations, the conditions for obtaining the best TiC coating layer were found to lie within a limited range. In this experiment, optimum conditions were found to be 0.17A for the EB emission current and 8.5×10^-4 Torr for acetylene pressure.

抄録全体を表示

A corrosion monitoring method is proposed using electrochemical techniques based on AC impedance theory. Monitoring corrosion rates by the AC impedance method with a low frequency response is time consuming. A method of monitoring to obtain corrosion rates easily by using a Lissajous figure technique with 60Hz commercial frequency was applied to pitting corrosion of SUS304 stainless steel in a neutral sodium chloride solution. The value of tanθ calculated from the inclination angle θ of the Lissajous figure was found to be related to pitting current density I at an impedance Z>1 by
tanθ=K·I K: const.
The relation between the value of tan θ and the corrosion rate was discussed in terms of reaction processes of charge transfer and diffusion.

抄録全体を表示

The relationship between the amount of chromium in oxide film and the amount of metallic chromium during electrodeposition was investigated by the galvanostatic and potentiostatic methods in baths containing various amounts of sulfate or nickel ions. It was shown that sulfate ion controlled the amount of chromium oxide and improved the deposition of metallic chromium. The most suitable SO₄/CrO₃ ratio for the deposition of metallic chromium were about 1/100. The effect of sulfate ion on the chromium oxide film was also observed by the current interrupter method. Sulfate ion decreased chromium oxide film resistance. The addition of nickel ions increased the current efficiency of metallic chromium deposition, and decreased that of chromium oxide film. These results suggested that metallic chromium is electrodeposited through the intermediate lower oxide of chromium during reduction to chromium of hexavalent chromium solution.

抄録全体を表示

Electroless nickel plating bath containing glycine and sodium citrate as chelating agent by means of deposition rate, bath life and phosphorous content in the deposited films was studied and simultaneous analysis of ions in plating bath by isotachophoresis was tried. Bath composition was; NiSO₄⋅6H₂O 30g/L, NaH₂PO₂⋅H₂O 30g/L, NH₂CH₂COOH 40g/L, Na₃C₆H₅O₇⋅2H₂O 20g/L, Pb(NO₃)₂ 2mg/L. Plating area was 400cm²; bath volume was 4L; and bath temperature 88±2°C. The supply solution was NiSO₄⋅6 H₂O 450g/L, NaH₂PO₂⋅H₂O 500g/L, Pb(NO₃)₂ 60mg/L. The deposition rate from this bath was 0.2-0.3μm/min, 2-3 times faster than the general malic acid bath. Bath life was more than 50 hours in continuous plating and about 6 turns could be obtained. Though phosphorous content in the deposited films depended on bath pH and the amount of sodiun hypophosphite, phosphorous content could be kept to 5-13wt% or 12wt% constant by adjustng the concentrations of nickel sulfate and sodium hypophosphite in the supply solution. Bath composition was so changed with plating that analysis of ions in the plating solution by isotachophoresis using 0.01mol HCl leading solution and 0.01mol sodium caproate terminal solution was tried. As a result of it, concentrations of hypophosphite, phosphite, phosphate ions and also of citric acid ion could be analysed simultaneously and with high precision.

抄録全体を表示

It was found that organic compounds which can form insoluble complexes with zinc in aqueous solutions may modify zinc surfaces to be resistant to corrosion. Two surface modification methods using 8-hydroxyquinoline [HQ] were found to improve corrosion resistance. In one method (the CT method) zinc is immersed in a neutral solution containing a small amount of HQ, and in the other (the SA method) zinc is anodized in the same type of solution. After CT, the surface consisted of bis (8-hydroxyquinolato) Zn (II) [ZnQ₂] which is insoluble in water but soluble in alcohol, and the corrosion of zinc was inhibited at an efficiency of about 90% in aerated chloride media of pH=4-10. The surface modified by SA was complex; the outer part was mainly composed of ZnQ₂ and soluble in alcohol, while the inner part which was insoluble in organic solvents consisted of an upper layer of complexes of Zn (II)-HQ-derivatives and a bottom layer of Zn (II)-oxyhydroxide. The inner part formed by SA showed good corrosion resistance even after removal of the outer part. The surfaces produced by CT and SA could be useful as an undercoat for paint, and CT can be used as a temporary protection of zinc as washing with alcohol will restore the metallic luster.

抄録全体を表示

Polyethylene terephthalate (PET) coated steel sheet was prepared by applying with adhesive a PET film 20μm in thickness on steel sheet that had been Zn-Co-Mo plated, and coated with polyvinylchloride (PVC), and its properties were compared to those of PVC coated and acrylic paint-coated steel sheet. In comparison with the other steel sheets, PET coated sheet was satisfactory in terms of such properties as corrosion resistance, adhesion strength after forming, chemical resistance, solvent resistance and denting resistance. The formability of PET coated steel sheet depended on the heating temperature at lamination, temperatures of 200-230°C being conductive to good formability. At temperatures above 230°C, mechanical properties deteriorate markedly, and at temperatures blow 200°C, adhesion strength between PET film and adhesive layer was insufficient. Recrystalization of amorphous portions occurs readily during slow quenching, resulting in deterioration of the mechanical properties. Thus quick quenching after lamination is indispensable to restrain the recrystalization. It is considered that the excellent corrosion resistance of PET coated steel sheet depends on the low water vapor permeability of PET film, and on the anticorrosive corrosion products of the Zn-Co-Mo plated sheet which reduce the anode reaction to less than that of Zn plated sheet.

抄録全体を表示