The following results were obtained in formation and morphology of galvanically substituted Au-film, which was precipitated and developed over iron surface by means of galvanic substitution of hydrochloric acid-auric chloride solution.
(1) In the earlier stage of precipitation, Au-film was developed in net-work, and then, slowly converted into plate crystals with the lapse of time. The substrate iron surface turned golden colored and was brightened in this stage, to which plate crystals of Au-film firmly adhered.
(2) When the iron surface was dipped in 0.1 or 3% hydrochloric acid-auric chloride solution, it was coated with plate crystals of Au-film within 30 or 0.5sec., respectively.
(3) The Au-film, after the lapse of time, consisted of plate and needle crystals, because the surface looked dark by irregular reflection in needle crystals.
(4) The defects of the plate crystals decreased and the growth of needle crystals were also retarded with the increase in concentration of hydrochloric acid in the solution.
(5) The defects of the plate crystals decreased, when the solution was agitated.
(6) The plate crystals, precipitated and developed over mechanically polished single iron crystals, were observed to be poly-crystals by means of electron diffraction. The microstructure of plate crystals grew in thick when they were precipitated on iron surface crystals having low values of Miller's indices, but they grew in thin when precipitated on crystals having high values.

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This paper reports the research on adhesion mechanism of electroless plating on ABS plastics under an electron microscope. Peeling test was conducted to determine the adhesive strength between copper and the plastics. It was indicated in normal plating conditions that peeling did not occur on the interface between plastics and metal, but on the surface layer of the plastics; and the adhesive strength depended upon the strength of the surface layer of the plastics. Hence, the molding and etching conditions of plastics had powerful effects on the adhesive strength. The above effects would be caused by the presence of internal stress and orientation in the contact part with the mold which made that layer concentrically brittle. The presence of such layer was observed under the electron microscope. The etching conditions had effects on the formation of dovetail joints. Stronger adhesion was produced by the formation of numerous joints under proper etching conditions. However, the parts of anchoring were limited on the whole, and chemical combination would also be taken into consideration for adhesion mechanism.

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The authors have studied on mechanical properties of aluminized steels and made experiments of aluminum coating on steels in expectation of good effects on prevention of stress corrosion cracking of the steels. At first, the effects of aluminum coating and heat treatments on stress corrosion cracking of 18-8 austenitic stainless steel were studied by dipping the specimens in 2 kinds of etching reagents; that is, boiling 42% MgCl₂ solution (b.p. 143°C) and boiling 20% NaCl solution (b.p. 102°C).
The results obtained were as follows.
1) As the results of rupture test of the specimens, the effects of heat treatments on stress corrosion cracking of 18-8 austenitic steel were not shown in boiling 42% MgCl₂ solution and its apparent threshold stress was about 10kg/mm². On the contrary, the effects of. heat treatments were remarkable in boiling 20% NaCl solution.
2) All the cracks of specimens were trans-crystalline in MgCl₂ solution and inter-granular in NaCl solution.
3) In aluminized 18-8 austenitic stainless steel, no rupture or etch pit was found after 200hr. test in MgCl₂ or 500hr. test in NaCl solution.
4) Weight loss in coated aluminum per unit area increased with the increase of applied stress and with the decrease of coated area of aluminum.
5) Current density between 18-8 austenitic stainless steel and coated aluminum in MgCl₂ or NaCl solution was higher than that which was required to prevent the steel from creating and propagating cracks.

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Effects of pH, temperature, and composition of bath on magnetic properties of deposited films were studied for two sorts of ammoniacal alkaline electroless cobalt plating baths.
The results obtained were as follows.
(1) The films deposited from ammoniacal alkaline baths had the maximum flux density (B_s) of about 9, 000 gauss, coercive force (H_c) of 200 oersted, and squareness of 0.5-0.7 in general. The variations in the above values of films depending upon plating conditions were found to be less than those of films deposited from caustic alkaline baths reported in the previous paper.
(2) In general, citrate bath (A-C type) was stable and gave films of higher squareness. However, the magnetic properties of these deposits greatly depended upon pH and concentration of complexing agents.
(3) Tartrate bath (A-T type) was less stable than citrate bath and generally gave films of lower squareness. However, the dependence of coercive force of these films upon the bath conditions such as pH and concentration of complexing agents was little.
(4) The difference in the effects of plating conditions of the both baths on the magnetic properties of films was systematically explained by each characteristics of the baths.

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