To reduce the probability of head-crash in higher density magnetic systems, new extremely thin protective layers against wear and corrosion must be applied on magnetic head-disk interfaces. In this study, dynamic deformation of properties lubricant and of lubricant and DLC (Diamond-like Carbon) film compound layer were evaluated by the force modulation method. With regard to hard disks coated with DLC film and PFPE (Perfluoropolyether), their surface dynamic deformation properties such as storage modulus, loss modulus and Tan δ, etc., have been evaluated by AFM (Atomic Force Microscope). Concretely, the characteristics of visco-elasticity related with the existence of lubricants on the valley and hill parts of the hard disk surface and these function after a micro-wear test were estimated with the force modulation method. The main results of above-mentioned tests are as follows.
[1] Viscosity properties like loss modulus and Tan δ of valleys are higher than those of hill. It is considered that the viscosity is corresponding to the existence quantity of lubricant.
[2] Micro-wear properties such as wear depth and wear volume of a PFPE coated disk are lower than those of the disk without PFPE.
[3] The wear of PFPE coated hard disks has shown that after micro-wear tests with a high load Tan δ in hill parts of surface is increased a little as evaluating its viscosity. On the other hand, Tan δ in the valley parts decreased under a high load in micro-wear test. It is thought that lubricants have been removed by the micro-wear test.

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Hydrophilic Ni-Zn alloy films were prepared by electrolytic composite-plating with Titanium oxide (TiO₂) fine particles. As the amount of dispersed TiO₂ particles in the plating bath increased, the amount of co-deposited TiO₂ increased and reached a constant value at 60 gdm^-3 of dispersed TiO₂: and the surface roughness and weight ratio of Ni atoms to Zn atoms also increased. The Ni-Zn/TiO₂ composite-plated film a showed higher contact angle against water droplets than the Ni-Zn plated film for the common measurement, although the TiO₂ plate prepared by the Sol-gel method showed a lower value than the other plated films. Two other measurements of contact angle employed suggested that a hydrated layer was formed on the TiO₂ particle surface and the adherent water on the layer spread over the composite-plated film surface. Then this spread water induced spreading area of the hydrated layer and consequently improved the wettability of the film surface. It was also implied that wettability of the film surface improved with the increase of co-deposited TiO₂ particles and the decrease of roughness with grinding. A composite-plated film by 4 wt% of co-deposited TiO₂ particles gave a 25 degree contact angle. The Ni-Zn/TiO₂ composite-plated film was found to have corrosion resistance equal to Ni-Zn plated films.

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Fatigue crack initiation and propagation behaviors under corrosive conditions were examined using high tensile steel specimens treated by Hot-Dipped Zn-5%Al and Zn-55%Al-1.6%Si alloy coating. Corrosion rate of the coating and the fatigue crack initiation in the steel were examined first. Then the sacrifice anticorrosive effect for the fatigue crack propagation was examined. As the result, the following conclusions were obtained.
(1) After the coating vanished, the corrosion rate of the base metal was slower than that of the uncoated case. Especially, the Hot-Dipped Zn-55%Al-1.6%Si specimen showed the slowest corrosion rate.
(2) The number of cycles necessary to initiate the fatigue crack in the coating vanished specimen is larger than that for the uncoated specimen.
(3) When the stress intensity factor falls below 31 MPa√m, the crack propagation rate by the use of Zn-55%Al-1.6%Si anode, becomes slower than that under atmospheric air condition.
From the above facts, the Hot-Dipped Zn-55%Al-1.6%Si alloy-coated steel exhibited excellent properties superior to the Zn-5%Al alloy-coated steel with respect to the initiation and propagation of corrosion fatigue crack.

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A novel Ni electroless plating method using Ti(III) as a reducer, which was characterized as a zero-emission process, was proposed. In this process, Ti(IV) formed during electroless plating reaction of Ni was electrolytically reduced to recycle Ti(III). This paper mainly deals with the electrolytic reduction behavior of Ti(IV) in a weak alkaline solution determined by cyclic-voltammetry measurement. Both Ti(IV) and Ti(III) are stable in soluble form in the pH range of 7 to 9 under the presence of complexing agents such as trisodium citrate and nitrilotriacetic acid. Cyclic-voltammetry measurements were made for Ni, Ti, Pb and Carbon felt, each was used as a negative electrode, and Carbon felt showed the most superior behavior as a negative electrode. It was demonstrated that electrolytic reduction of Ti(IV) was possible in a weak alkaline solution of pH 7 to 9 in the presence of trisodium citrate and nitrilotriacetic acid, obtaining 65% regeneration efficiency. However, if the Ni(II) ions remained in the plating solution it interfered with current efficiency by preferentially plating Ni on the Carbon felt electrode, evolving hydrogen gas. To avoid such trouble, it was proposed that the concentration of Ti(III) be increased to twice the Ni(II) concentration or that of pH 0 waste solution be applied.

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