An experimental study of electroless cobalt-zinc-phosphorous plating films is presented. The results obtained are as follows; 1) The zinc content of the cobalt-zinc-phosphorous films varied from 0 to 11% with zinc sulfate concentration in the solution. 2) Cobalt-zinc-phosphorous films exhibited coercive force ranging from 1600A/m (20 Oe) to 88000A/m (1100 Oe) depending on the plating conditions and high coercive force above 80000A/m (1000 Oe) was achieved for 10μm thickness films. 3) Incorporation of zinc into the cobalt-phosphorous films changed its structure such as particle size, anisotropy and isolation of particles. The modification of magnetic properties could be explained in terms of these film structure changes.

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The electric resistance behavior of chemically deposited Ni-P, Ni-B, and Ni-W-P alloy films at the initial deposition stage and with the heat treatment was investigated by means of film resistance measurements, X-ray diffraction analysis, and differential scanning carolimetry. At the initial deposition stage of the as-plated nickel alloy films, the stability and uniformity of electric resistance of Ni-W-P film were extremely superior to those of Ni-P and Ni-B films. The structural variation of Ni-P film was recognized at the lowest heat treatment temperature, while that of Ni-W-P film occurred at the highest heat treatment temperature. The stability of electric resistance of the films corresponded well to the structural variation with the heat treatment.

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Corrosion fatigue strength of electroless Ni-P steel was investigated by rotating bending fatigue test at 0.6 and 60Hz in dropping 3% NaCl solution. The changes of microstructure of Ni-P film by cyclic stressing were examined by X-ray technique. 1. Ni-P film keeps amorphous structure and exhibits an excellent corrosion resistance regardless of the presence of applied stress. 2. Since a pre-microcrystalline forms in Ni-P film by cyclic stressing, the corrosion resistance decreases, accopmanied by negative shift of the corrosion potential. 3. The corrosion resistance of the plated layer decreases with increasing the number of cyclic stressings or local crystallization. Then corrosion pits were produced on the surface, stress concentration is induced at the bottom of pit and then the pit grows up to corrosion fatigue crack. 4. The corrosion fatigue life of steel was improved by about 50 percent by Ni-P plating, which is not as much as was expected for the amorphous metal.

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Ni-P deposits with phosphorous content ranging from 0 to 15.7wt% were plated onto iron sheet from Watts-type bath containing different amounts of phosphorous acid. The corrosion resistance of the electro-deposited Ni-P alloys was studied by the Corrodkote test, immersion test, electrochemical measurement and scanning electron microscopy (SEM). The results are summarized as follows. (1) Corrosion resistance of the as-deposited Ni-P alloys containing 5.3wt% phosphorous was found to be most inferior in the Corrodkote and immersion test. With increasing phosphorous content in the as-deposited alloy, the corrosion resistance increased. Ni-15.7wt%P alloy showed the most superior resistance. Corrosion resistance of the heat-treated Ni-P alloys increased with an increase in the phosphorous content, and Ni-15.7wt%P alloy showed excellent resistance. (2) Natural corrosion potential of the as-deposited Ni-P alloys containing more than about 10wt% phosphorous showed the more noble potential in the Corrodkote solution. (3) Anodic polarization behavior of the Ni-13.4wt%P in the Corrodkote solution was remarkably different from that of amorphous state (as-deposited) and crystal state (heat-treated), that is, the anodic polarization curve of amorphous state shifted toward more noble potential than that of crystal state.

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This report describes the effects of both trivalent chromium content in the chromium bath and current density on the preparation of the electrodeposited amorphous chromium and describes the preparation of electrodeposited amorphous chromium binary alloys. The amorphous chromium bath was prepared by using the Cr-W alloy bath without W ions as a basic bath. Amorphous Cr film was deposited at 2.1×10⁴A/m² from this chromium bath which contained 50% of trivalent chromium. Because these conditions on the preparation of amorphous Cr films are very different from those on the preparation of ordinary Cr films, authors investigated the effects of both trivalent chromium content in the chromium bath and current density on the microstructure of chromium films by transmission electron microscope. It is found from this investigation that amorphous Cr films were electrodeposited from the baths containing trivalent chromium of more than 40%. In the case of 40% trivalent chromium bath, the microstructure of Cr films varied from a single amorphous phase to an amorphous phase containing cubic crystals with an increase in current density. In the case of the 50% trivalent chromium bath, all the chromium films were amorphous, regardless of the current density. Amorphous Cr-W and Cr-Mo binary alloys were deposited from the 50% trivalent chromium baths containing various amount of W ions or Mo ions. The W and Mo contents in the amorphous chromium binary alloys were up to 7.8at% W and 12.3at% Mo, respectively.

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This report describes the crystallization processes of the amorphous Cr and the amorphous Cr-Mo binary alloys which were prepared by the electoroplating method. The crystallization processes of the amorphous Cr and the amorphous Cr-Mo binary alloys were investigated by differential thermal analysis (DTA) and transmission electron microscope (TEM). The crystallization onset temperature of the amorphous Cr, Cr-2.3at%Mo, and Cr-5.2at%Mo alloys were 773K, 838K, and 878K, respectively. The rise of crystallization onset temperature by the addition of Mo indicated that the molybdenum contributed to the thermal stability of the amorphous Cr. The cubic crystals of about 30nm diameter, which were the b.c.c. chromium single crystals consisting of six {001} planes, precipitated in the initial crystallization stage of the amorphous Cr. In the perfectly crystallized chromium film, numerous micro twins were observed in the original amorphous region which the cubic crystals did not precipitate. The crystallization process of the Cr-2.3at%Mo alloy was similar to that of the amorphous Cr except for the next two phenomena. The one phenomenon was that the size of precipitated cubic crystals was about 80nm diameter, and the other was that density of micro twins was more than that of the amorphous Cr. It was found from the measurement of lattice constants that the crystals precipitated in Cr-Mo alloys were stable solid solutions.

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The solderability properties of electroless nickel-phosphorous alloy and nickel-tin-phosphorous alloy films deposited by sodium hypophosphite as a reducing agent were studied using quantitative contact angle and spread factor measurements with reference to the effect of the phosphorous and tin contents of alloy films. Two kinds of solder balls, 60/40 (tin/lead), containing 2% resin and dropped enough flux, 1mm in diameter were used for solderability test at 210°C. It was found that nickel-phosphorous alloy films containing about 7% phosphorous provided best solderability properties of nickel-phosphorous films. With regard to the particle size, good solderability was obtained as the particle size decreased and thus the deposit was amorphous. It was also found that nickel-tin-phosphorous alloy films provided better solderabilities with increasing tin content of the alloy films.

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