Stress, hardness, and elongation of duplex nickel plating electrodeposited in Watts bath by adding
(1) butynediol+CH₃COOH
or (2) coumarin+HCHO
were measured, and the following results were obtained.
(1) The plating deposited in Watts bath by adding butynediol only was a bright plating with greater stress (40-70×10³psi), higher hardness (400-600Hv), and less elongation. When 2g/l or more of CH₃COOH was further added to the above bath, semi-bright nickel plating with less stress (10-15×10³psi), lower hardness (200-250Hv), and greater elongation was obtained.
(2) Stress of the plating deposited in Watts bath by adding coumarin only was less than that deposited in Watts bath with no additives. However, when more than 0.01g/l of coumarin was added, hardness increased to higher than 500Hv. When coumarin added was less than 0.01g/l, semi-bright nickel plating with greater elongation was obtained and when a small amount of HCHO was further added, the plating was more improved.
Appropriate conditions of the electrolysis were at pH=4.0, temperature=50°C, and with air agitation. When pH and temperature were higher, bright nickel plating with greater stress, higher hardness, and less elongation was obtained.

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Corrosion resistance and porosity of electroplated bright tin coating on steel substrate were evaluated by salt spray test and modified ferricyanide test, and the results were compared with those of other tin coatings.
Effects of diffusion of brass substrate in the electrodeposited coating were studied by sulfur dioxide test, microsection observation, and X-ray diffraction method. The results were as follows:
1. Porosity of bright tin plating was lower and its corrosion resistance was higher as compared with other tin coatings.
2. At places, where steel was exposed in pores of electrodeposited tin, oxygen was expelled from the corrosive solution and electrochemical behavior might be reverse. It was considered that the dissolution of tin was very little; because it was anodic to steel which was made unattached.
3. Tin salts such as SnCl₂ were converted to precipitated stannous oxychloride by absorbing liquor. Stannous oxychloride was insoluble in water and inhibited exposed steel from corrosion by sealing up capillary tin pores.
4. Diffusion rate of zinc from brass substrate into tin coating was very higher than that of copper. The both diffusion rates were higher as compared with other tin coatings. The reason of higher diffusion rates in electrodeposited bright tin would be due to its fine crystals and richness in grain boundary.

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In general, it is considered that corrosion resistance of plating depends upon the varieties and thickness of plating. Moreover, the appearance of rusting is varied with test methods.
The experiments were conducted to investigate the correlation between the corrosion tests by salt spray, CASS, corrodkote, etc. and the exposure in the outdoor air; and also to determine the best method for testing duplex nickel plating.
The results were as follows:
i) Corrosion resistance of duplex nickel plating is higher than that of single nickel plating.
ii) In duplex nickel plating, minimum thickness of 20μ is required for high resistance.
iii) Copper plating, which is the substrate of duplex nickel plating, has no correlation with the resistance.
iv) The most intimate correlation between accelerated corrosion test and outdoor exposure is seen in corrodkote test.
v) When the corrosion degree is very low or very high, rating number corresponds well with the percentage of corroded area (by section method), however, when it is in the middle degree, there is no correspondence between the both.

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