Undercoat plating for high density thin-film memory disk was studied for its relevance in perfecting mass production of hard disks. It was found that the plating operation had to be considerd as a system and not a series of individual components. The equipment and environment of the plating operation are as important as the plating solution. The authors recommend ultra fine filtration, water purity, rinsing, equipment design, automation of the analytical equipment and the plating environment, as essential elements in mass production, thereby achieving fully systemized undercoat plating developed providing highquality mass production.

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The porous Al₂O₃ film formed by anodizing 99.99% Al in 10 wt% sulfuric acid solution was colored electrolytically in 6.3×10^-3mol potassium permanganate solution at 27V AC 50Hz for 1min. Mn compounds were electrodeposited at the bottom of pores during electrolytic coloring of the film. When the colored film was re-anodized in 0.1mol ammonium pentaborate solution at a constant direct current density of 20A/m², an intensive yellow emission was observed on its surface. Since the barrier oxide layer thickens during re-anodizing, it is considered that Mn²⁺ is incorporated within this layer and acts as the electroluminescent activator.

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Zirconium-type chemical conversion coatings were studied as a pretreatment of the organic coatings on the surface of aluminum cans. The structure of the chemical conversion coatings and adhesion capability on to the organic coatings were investigated by using Auger electron spectroscopy (AES). Chemical conversion coatings consist of a layer that is mainly composed of PO₄ on a solid-liquid interface, although the layer is chiefly composed of chemical compounds of PO₄ and Zr or Al. It was found that aluminum oxide (or hydroxide) and aluminum fluoride are present at the interface between chemical conversion coatings and the aluminum substrate. The mechanism of development the chemical conversion coatings can also be considered as the result of a solid-liquid reaction between chemical conversion coatings and the liquid phase. The composition of chemical conversion coatings reflects the composition of the solid-liquid interface, and when the concentration of Al or HF in the bath is high the quantity of Al in the chemical conversion coatings increases. It is concluded that the reasons for the good adhesion between zirconium-type chemical conversion coatings and phenolic-epoxy systems are the penetration of the macromolecure chains composing the organic coating into the chemical conversion coatings, as well as interaction between the functional groups of macromolecular chains and Zr, PO₄ and their compound which may be formed in the chemical conversing coatings.

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The shift in the Mn content of zinc phosphate crystal films on cold rolled and galvannealed steels and the changes in anti-alkaline properties were investigated at varying concentrations of Mn²⁺ ion in zinc phosphate solutions. At Mn²⁺ ion concentrations from 0 to 2500ppm, the changes in the Mn content of the zinc phosphate crystal films formed were confirmed to be in accordance with the Mn²⁺ ion concentration, with Mn content reaching 6wt.% of Hopeite crystal film on galvannealed steel and 8wt.% of Phosphophyllite crystal film on cold rolled steel.
It has previously been clarified that the Mn²⁺ in the solution acts to modify the chemical structure of zinc phosphate crystal films, and that the modified structures were Zn_3-xMn_x(PO₄₎₂⋅4H₂O for Hopeite and Zn₂(Fe_1-xMn_x)(PO₄₎₂⋅4H₂O for Phosphophyllite. As it was predicted that the anti-alkaline properties of these films would change accordingly, the loss in weight of zinc phosphate crystal films through the action of NaOH solutions adjusted to pH 10.5, 12.0 and 13.0 was discussed. At all values of pH, the weight loss of Hopeite crystal film exceeded that of Phosphophyllite, but the absolute values of weight loss decreased in accordance with Mn²⁺ ion concentration, i.e., with the Mn content in the zinc phosphate crystal films. The decrease in weight loss, i.e., the improvement in anti-alkaline properties was remarkable in the high alkaline region around pH 13.0.

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An investigation was carried out on the thermal shock resistance of CaO-ZrO₂ (calcia stabilized zirconia or CSZ) coatings produced by water plasma spraying, a newly developed process for producing ceramic thermal barrier coatings (TBC) at a lower running cost. TBCs produced by WPS consist of a bond coat and a ceramic overlay. A substrate a 304 stainless-steel was coated with a NiCrAl bond coat by gas plasma spraying (GPS) and CSZ powder was then applied by WPS. Excellent thermal shock resistance was obtained very efficiently. Particle size was found to be between 53-105μum, and optimum thickness was achieved both for the bond coats (0.3-0.4mm), and for the CSZ coatings (0.4-1.0mm).
These WPS coatings showed better thermal shock resistance than GPS coatings because of their moderate porosity. Phase analysis of the ceramic overlay and of the interface between the bond coat and the overlay were carried out by XRD and EPMA, and the degradation mechanism was studied.

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An increase in particle velocity generally may result in denser coatings with higher bonding strength. Based on this fact, a new flame jet spray method has been developed to produce high-velocity particles. Coatings made by this method showed higher tensile strength, higher density, lower porosity and higher hardness.

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