The effects of KAu(CN)₂ concentration and cathodic current density of the bath on the grain size and twin frequency of gold deposits obtained from the citrate baths, A and B in the previous paper, were studied.
The results obtained were as follows:
1) The grain size of gold deposits obtained from the bath A increased with current density and decreased with KAu(CN)₂ concentration. It also increased with the thickness as expressed by the formula:
Gs=K′lnT+K″. (where Gs: grain diameter, T: thickness, and K′ and K″: constants depending on plating conditions)
It was also found that twin frequency increased with grain size.
2) The bath B was more effective than the bath A in controlling the grain growth. Therefore, it was found that the structure of gold deposits on copper substrate from the bath B agreed with the structure of the substrate and the positions of twins observed in gold deposits agreed with those in copper substrate.
Most of crystal grains of gold deposits were single crystals and the direction of bands observed in them was always [111] without exception. It was supposed that gold was preferentially deposited in the direction of the highest atomic density in the early stage of deposition.
3) The presence of twins in grains had greater effects on mechanical strength of deposits with the increase of twin frequency in the same grain size. Therefore, it was found that the twin frequency, which increased with the increase of grain size, had effects on mechanical strength of gold deposits.

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In order to develop a shop primer for giving the highest weldability and gas-cutting ability of steels, experiments were conducted on the steel coated with various kinds of shop primers.
The employed shop primers included 70 kinds. Their groups and kinds were as follows:
20 kinds……prepared by the combinations of various resins and pigments
22 kinds……prepared by the combinations of phenoxy resins and various pigments
6 kinds……prepared by various PVC (volume concentration of pigment) value
4 kinds……prepared by various compositions of solvents
6 kinds……for various coating thicknesses
12 kinds……for several commercial shop primers
The coating thickness of primers was about 25μ, except for the above 6 kinds which were in the range of 10-40μ.
Blank tests were conducted for reference on the uncoate3 steel.
Arc welding was carried out by manual and butt weld.
Welding usability test and bead appearance test, X-ray inspection, tension test, roller bending test of the weld zone, and gas cutting ability test were carried out on these test pieces.
The results obtained were as follows:
1) Phenoxy resins showed considerably superior weldability of steel; but chlorinated rubber resins, acrylic resins, and pigment of lead type were inferior. Generally speaking, the effects of shop primers on weldability of steel seemed to be somewhat different according to the combinations between resins and pigments.
2) Non zinc shop primers, D and E, showed the highest weldability and cutting ability among 70 kinds of the primers.
3) The commercial shop primers showed superior weldability to trial primers.
4) Chlorinated rubber resins showed the lowest gas cutting ability. Phenoxy, alkyd, and ketone resins showed fairly high cutting ability.
5) The commercial shop primers, except for those of zinc rich type, showed fairly high gascutting ability.
6) The effects of coating thickness of weld on welding and gas-cutting were not observed in such a narrow range of 10-40μ.

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Corrosion behavior of galvannealed steel was studied under various corrosive circumstances and was compared with that of galvanized or electrogalvanized steel.
The results obtained were as follows:
1) The corrosion rate of galvannealed steel was lower than those of other zinc plated steels.
2) The coating layer of the galvannealed steel was composed of Fe-Zn alloy (mainly of δ₁-phase) and its natural electrode potential was nobler than those of other zinc plated steels.
3) Zinc of the coating layer was preferentially dissolved by corrosion so that iron was enriched on the coating surface to be converted into red rust, which prevented the internal zinc from dissolution. However, it took a longer time for the substrate metal of galvannealed steel than other zinc plated steels to be corroded into the red rust. Therefore, it was concluded that the coating layer of galvannealed steel has very high corrosion resistance.

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Au plate crystals were prepared on iron substrate by means of electroless plating using sodium hypophosphite as a reducing agent and their microstructure was investigated by direct electron microscopy and electron diffraction.
The results obtained were as follows:
1) Two kinds of rotational moiré patterns were observed in the Au plate crystals. One pattern was observed on the subboundary of the crystals, and the other was observed covering fine particles which had grown up on the crystals. In the stage of crystal growth, the stress due to lattice defects in the crystals was relaxed by the rotation of these particles.
2) Electroless plated Au plate crystals contained many micro-twins which contributed to relax the stress. These micro-twins were formed in the initial stage of crystal growth. The width of micro-twins increased with the thickness of the crystals, but the length was independent of the thickness.

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