The effect of additive coumarin on the electrodeposition of nickel from Watt's bath was studied using impedance measurement. The crystal orientation of the deposits was investigated by X-ray diffraction (XRD) and their morphology by scanning electron microscopy (SEM). Coumarin inhibits nickel electrodeposition, increasing the charge transfer resistance and decreasing the double layer capacitance in impedance diagrams. At current densities of 200A·m-2 and 400A·m-2, the deposits had a (200) preferred orientation structure, changing to (220) when the current density was 800A·m-2. Coumarin influenced the relaxation of the electrode coverage by an adsorbed intermediate such as (NiOH)ads and caused an increase in size of the low frequency loop, enhancing the preferred orientation as coumarin was added. Coumarin also has the effect flatting the crystal, preparing denser deposit.
TiN film was coated onto SK 5 substrate by RF ion plating under different bias voltages, and X-ray diffraction analysis and ESCA measurement were performed on this film to determine the X-ray intensities of the (111) and (200) planes and the composition of the film. To evaluate the orientation of the TiN film using this X-ray intensity and composition data, the relation ship between the composition and the X-ray intensity ratio of the (111) plane to the (200) plane for randomly oriented TiN (TiC) was investigated. It was found that the composition of the TiN (TiC) affects the X-ray intensity ratio, and that the orientation of the film changed with the bias voltage. The composition also affects the packing density of each plane and, therefore, is considered to be one of the parameters which influences the orientation of the film. In addition, the orientations of previously reported TiN and TiC films coated by the PVD method were re-examined.
The corrosion resistance of 18-8 stainless steels coated with TiN formed by a hollow cathode discharge (HCD) type ion plating process has been studied by using mainly electrochemical means in sulfuric acid solutions. The influence of the sulfide (MnS) inclusions on the intercepting effect of the TiN film from its surroundings was also estimated. In specimens having greatly diminished MnS content, a homogeneous. film was formed on the steel regardless of the Mn/S ratio in the steel. In specimens with a large MnS content, on the other hand, a homogeneous film can be formed by decreasing the Mn/S ratio. Thus to improve the corrosion resistance of the TiN coated steels, it is necessary to diminish the MnS content and decrease the Mn/S ratio. The starting points of corrosion of the TiN coated steels were film defects formed on the MnS inclusions. In steels with a small amount of MnS and a low Mn/S ratio, spalling of the TiN films scarcely occurred, and corrosion resistance was excellent. When the Mn/S ratio was low, the surface of the MnS after ion bombardment was smooth because the MnS was practically unaffected by physical attack of argon ions. Consequently TiN films formed on the MnS contained hardly any defects, and are superior in terms of the intercepting effect from the environment.