The physical properties of electrolytic Ni-Co-P deposits have been investigated. The results obtained are reported in this paper as follows.
The hardness of the deposited films after heat treatment was measured with a Micro-Vickers hardness tester. The maximum of hardness was observed at about 400°C. When the desposits were heat-treated at above 400°C, they showed a tendency to toward softening. However, the above tendency depended upon the cobalt contents.
It was observed by X-ray diffraction patterns that both of Ni and Co phosphides had been produced by exothermic change in both of the electrolytic Ni-Co-P deposits and the compacts of mixed powders.
The formation of Ni-Co solid solution was also identified by X-ray analysis in electrolytic Ni-Co-P deposits during the heat treatment at 500°C.

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Corrosion inhibition of iron in perchloric acid solution by the compounds containing oxygen (such as alcohols, ketones, aldehydes, organic acids, etc.) was investigated from the electrical double layer capacity values at the metal-solution interface, polarization characteristic curves, gravimetric corrosion tests, etc.
As the results, it has been known that the inhibition mechanism of the above compounds are classified into the following three categories with respect to the chemical kinds of the compounds.
(1) Alcohols and acetones are electrostatically adsorbed on iron as cations.
(2) Organic acids are adsorbed on iron as anions.
(3) Aldehydes seem to be polymerized at the interface and the polymer thus formed inhibits the corrosion by interrupting the diffusion of corrosive substances to the electrode.
It would be concluded, therefore, that the adsorption of the compounds containing oxygen atoms is not directly caused by the lone pair electrons of oxygen as it was so concerning the compounds containing N- or S- atom.

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There have been no complete researches on the crystal structure of black chromium deposit from the plating bath containing hydrogen silicofluoride. The authors studied these crystal structures by microstructures and electron diffraction pattterns for explaining relationship between physical properties and structures of the deposits.
As the results, it was found that the black chromium plating layer consisted of laminated structure, in which the upper layer was peeled off from the lower one. The upper layer was a black deposit consisting of Cr₂O₃ which contains Cr (body-centered cubic). However, these crystallizations depended upon plating conditions; when the bath temperature and current density were higher, the crystallization was more accelerated and the growth of single crystals (Cr₂O₃) was also more developed. In these conditions, deposits were likely to be more easily cracked owing to the growth of other complicated chromium oxides or metastable hexagonal chromium crystals on the boundaries of these Cr₂O₃ single crystals.
The lower layer was a grayish black thin layer, consisting of Cr₂O₃ of body-centered cubic lattice or hexagonal system which contains various other chromium oxides.
Cr₂O₃ had crystal structure of hexagonal system and was cleaved along (100) plane and peeled off on (001) base plane.
Hardness and abrasion resistance of the black chromium deposit depended upon composition and structure of these crystals, and the cracks of the deposit were formed along the cleavage planes of Cr₂O₃ single crystals.

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The formation of polymer film onto steel plate was carried out by the same process as onto aluminum plate. The authors investigated on the formation of adherent film of copolymers from acrylonitrile and other vinyl monomers. As the results, the coulomb efficiency for the formation of adherent polymer film did not depend on the kind of metal used as cathode. The ascending order of coulomb efficiency was arranged as follows:
AN-VAc<AN<AN-MMA<AN-MA<AN-αMSt<MST<AN-ST
<AN-EMA<AN-EA<AN-BMA<AN-BA
However, in most cases:
aluminum>stainless steel>iron
The above results show that the electrode metal has effects on the formation of polymer with reference to the source of electron and for covering the area of deposition.

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The growth of oxide film on 1100 aluminum in water was examined at 30-100°C. The initial corrosion product consisted of boehmite and thicker film of bayerite was formed on the surface at below 84°C. However, the film formed at above that critical temperature consisted of single boehmite.
The rate of film formation reached a maximum at 60°C. However, bayerite was likely to be formed thicker at lower temperature.
The corrosion gave rise to pitting which was caused by compound particles in aluminum and concentration cell due to dissolved oxygen in water. The pitting action was soon ended when the compound particles were separated from the substrate aluminum by dissolution of the latter. Thus, all the pits remained in microscopic size.
Aluminum was colored black at below 50°C by roughness of the metallic surface due to corrosion. The coloring was not uniform and white rings developed around the pits. These rings would be formed by the change in pH brought about by the pitting action.
Many fine particles consisting of secondary phase of aluminum were seen on the film formed at 60-80°C. Then, the specimen was colored brownish gray owing to these particles.

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Surface treatments were conducted on aluminum alloy ADC 12 by chemical tin plating, electroless nickel plating, molybdenum disulfide coating on zinc phosphating, and hard anodizing. Then, frictional and wear resistances of the above treated surfaces were studied.
The results obtained were summarized as follows.
(1) These treated surfaces showed particularly lower coefficients of statical friction by preventing adhesion of metallic substances.
However, the combinations of the platings of the same kind, such as tin plating with electroless nickel plating, showed higher coefficients of statical friction.
(2) Molybdenum disulfide coating had the most remarkable effects on lubrication and tin plating was the second.
(3) It was found by wear test that these treated surfaces showed higher wear resistances than those of no treatment.
(4) Molybdenum disulfide coating showed the highest wear resistance.
(5) Electroless nickel plating and hard anodizing showed the next highest wear resistance. However, these surfaces considerably weared out the other contacting metal when they were combined with other metals. In particular, hard anodizing had remarkable effects.
Therefore, it was found that anodizing is not a proper surface treatment if the treated surface is used in combination with a soft metal such as an aluminum alloy.
(6) Tin plating was not very effective in surface treatment for rotors, because it gave thin film showing low wear resistance.
On the other hand, tin plating was very effective for stators, because of higher wear resistance. The combination of tin plated surface on the stator and molybdenum sulfide coating on the rotor showed higher wear resistance than any other combinations.

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