It was found that Fe-Al alloy layers were formed on the surfaces of steel specimens, when the specimens were dipped in molten lead bath containing a liquid solution of 0.12-0.5 wt% Al at 650-900°C for 5-60min.
The thickness of the alloy layer increased with the increase of aluminum content of the lead bath and with the rise of bath temperature.
The weight loss of steel specimens during dipping in a lead bath was much less than that dipped in an aluminum bath.
Metallographic observation and X-ray microanalysis revealed that the alloy layer formed in the lead-aluminum bath was composed of two layers as that formed in the aluminum bath. The layer adjacent to the steel was assumed to be Fe₂Al₅ and the outer layer was to be FeAl₃.
A uniform cover of Fe-Al alloy layer was observed on the surface of the steel specimens when they were dipped in Pb-20 wt% Sn bath containing aluminum at a relatively low temperature of 600°C as that observed by dipping in a lead bath at 700°C.

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The effects of various impurities on the internal stress of iron deposits were investigated. The Brenner-Senderoff contractometer was used to measure internal stresses in all determinations.
The results obtained were summarized as follows
1) The curve of manganese represented that the stress was decreased with the concentration in the early stage, but it was increased when the concentration was over 0.5g/l.
2) Nickel linearly increased the stress. The deposit produced by the addition of nickel was brighter than the normal deposit. It was difficult to peel the deposit from the helix with hydrochloric acid, which indicated the possibility of co-deposition of nickel with iron.
3) Chromium and copper had little effects on the stress in the range of concentration studied. The deposit gradually became darker with the increase in the concentration of the impurity.
4) Zinc and tin(II) linearly increased the stress at a high rate. The structure gradually became finer with the increase in the concentration of addition agent.
5) Boric acid and urea decreased the stress. Whereas, sulfates increased the stress.
6) Chlorides had abilities of increasing stress. The addition of ferrous chloride increased the stress in proportion to its concentration.

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The effects of polarization characteristics on current efficiency of chromium plating bath were studied and the following results were obtained:
1) In the solution containing fluorides, the electrode reaction for electrodeposition of metallic chromium plating was retarded, and the intermediate products in cathodic reduction such as black chromium plating were likely to be deposited so that the increase of current efficiency was inhibited.
2) In the solution containing fluorides, the electrode reaction for electrodeposition of metallic chromium plating was more detarded with the drop of the bath temperature, and the deposition of intermediate products in cathodic reduction was likely to be promoted so that the increase of current efficiency was inhibited.
3) In the solution containing sulfuric acid, the current efficiency was greatly increased with the drop of the bath temperature.
4) In the solution containing the mixture of sulfuric acid and fluorides, the current efficiency of the mixed solution was likely to make a compromise between the both efficiencies of each of solutions containing sulfuric acid and fluorides, respectively.

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The reduction processes of Pd(II) with Sn(II) in hydrochloric acid, which constitute main reactions in sensitization and activation, were investigated as a fundamental study on the metallization of plastics.
The reduction processes and the behavior of intermediates were pursued by means of potentiometric, spectrophotometric, and polarographic methods.
The following results were obtained:
1) In the course of reduction processes, the complex ions in the form of [Pd(II)Sn(II)_mCl_x]^n- (in which m=2 and 6) were formed. The complex ions of m=6 were more stable than those of m=2 with the increase in the ratio of Sn(II)/Pd(II) and Cl^- concentration in the solutions.
2) These complex ions were gradually decomposed by the intramolecular redox reaction of Pd(II) with Sn(II) to form free Pd(0) and Sn(IV).
3) The substance which acts as an active site in the electroless plating process was assumed to be the negatively charged metallic palladium colloid, which was formed by the above intramolecular redox reaction and was stabilized by adsorption of Sn(II).

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The diffusion coefficients of chromium in 11 Ni/18 Cr stainless steel (AISI 329) were determined over a temperature range of 1050-1150°C as a sudy of the 1st stage on the diffusion coating of electroplated chromium.
The results obtained were summarized as follows (in the unit of cm²/sec.):
1050°C D=7.91×10^-10(0.39 Cr)-2.55×10^-11(0.80 Cr)
1100°C D=6.32×10^-10(0.45 Cr)-2.11×10^-11(0.90 Cr)
1150°C D=2.73×10^-9(0.35 Cr)-4.50×10^-11(0.91 Cr)
The results nearly corresponded with those obtained in Fe-Cr system. Therefore, the chromium diffusion in 11 Ni/18 Cr stainless steel would be assumed to be approximately equal to the diffusion of Fe-Cr system.

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