For the estimation of the thickness of electrodeposited layers on metal, the theoretical equations of fluorescent x-ray intensities, in which excitation efficiencies and mass absorption coefficients were treated as a function of wavelength, were derived by the following three methods. (1) The method using the intensities of fluorescent x-ray radiated from electrodeposited layers......Method-1, (2) The method using the intensities of fluorescent x-ray radiated from substrate materials......Method-2, (3) The method in which an excitation effect in the method-2 is considered. The samples prepared in this study were Ni electrodeposited on Cu substrate, Ni on Fe and Cu on Fe. The thickness of the electrodeposited layers ranged from 1 to 35 microns. The calculated values by the equations were compared with the measured fluorescent x-ray intensities and the following results were obtained. (a) Measured and calculated intensities were in good agreement when the layer was thinner than a certain value. Consequently the thickness of the electrodeposited layer can be determined in this range using the calculated x-ray intensities and the fluorescent x-ray intensities from materials much thicker than several tens micron. (b) The maximum thickness of electrodeposited Ni layer which can be measured by the method-1 was 30, 26 and 19 microns when the supplied voltages to tungsten x-ray tube were 30, 20 and 15Kv respectively. The thickness of Ni on Cu by the method-2 was 39, 32 and 26 microns respectively. (c) When fluorescent x-ray from the electrodeposited layer caused the excitation effect to substrate materials, the effect showed a maximum at a certain thickness of the layer, 5 microns for Ni layer on Fe substrate.

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In the electrochemical machining of steels in NaNO₃ and NaClO₃ electrolytes, it is well known that oxide films are formed on the surface at low current densities. The effects of physical and chemical properties of the oxide films upon machining precision was investigated for various steels and electrolytes at different current densities. Thickness, electric resistance, surface roughness and chemical composition and other properties of the oxide films were measured by use of X-ray fluorescent spectroscopy, a SQ meter, a proficorder and electron diffraction. For NaCl electrolyte, oxide film is not formed. For NaNO₃ and NaClO₃ electrolytes, porous oxide films, about 1μm thick, are formed on steels surface. Electric resistance of the oxide films decreases with an increase in the current efficiency. The chemical compositions of the oxide film on S45C steel were determined to be Fe₃O₄ for NaNO₃ electrolyte and γ-Fe₃O₄ for NaClO₃. The films in NaNO₃ were more conductivity than that in NaClO₃. It was found that the current efficiency depends on mainly electric resistance of the oxide films formed on steels surface.

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Ni-P alloys with phosphorus content ranging from 0 to 16.2wt% were electro-deposited from Watts-type bath containing different amounts of phosphorous acid. The effects of the phosphorus content and the heat-induced structural change of the alloys on acid corrosion resistance were studied by electrochemical measurements and immersion tests in 1kmol/m³ HNO₃, 1kmol/m³ HCl and 0.5 kmol/m³ H₂SO₄ solutions. Surface observation of the alloys after the immersion test was also carried out using an optical microscope. The results are summarized as follows. (1) Corrosion resistance of the deposited alloys immersed in the HNO₃ solution increased with an increase in the phosphorus content. On the contrary, corrosion resistance of the alloys in the HCl and H₂SO₄ solutions decreased with an increase in the phosphorus content up to -5wt%, but increased when the phosphorus content exceeded -5wt%. (2) Passivation of the deposited alloys with phosphorus content of 4.1wt% or above did not occur on anodic polarization in the HNO₃ and H₂SO₄ solutions. (3) Corrosion resistance of the alloys containing 8-12wt% P, which had been heated up to 603K, was found to be excellent when immersed in these three acid solutions. This superior corrosion resistance seems to have some important bearings on heat-induced structural change of the alloys. The surface appearance of these alloys remained bright after being immersed for 120 days in these three acid solutions which were kept at 293K.

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The rate of covering an iron surface with electrodeposited zinc has been determined by the measurement of permeation rate of hydrogen which was done with an electrochemical technique. The use of parameter, K' or m' that characterize the covering rate of surface was proposed based on an assumption of linear or expotential decrease of hydrogen concentration on the surface of iron with time. Such parameter could be determined from the time at which the permeation rate reaches the maximum value. The K′/i values which means the covered area per unit amount of electric charge were measured in zinc sulfate bath. They decreased with the increasing current density significantly and then reached a constant value.

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