Using amino acids as additives, Ni films were fabricated by electroplating in a Watts bath. The amino acids affected the Ni film composition, surface morphology, crystal structure, hardness, and the codeposition mechanism.
The addition of S-containing amino acids such as methionine, aromatic amino acids such as tryptophan, and basic amino acids such as lysine, histidine, and arginine to the plating bath led to incorporation of C with the Ni films. The C contents in the plated film increased. The grain size decreased concomitantly with increasing amino acid concentration in the plating bath. The Ni film hardness increased with grain size refinement up to 10-15 nm. Maximum hardness of about 500-550 Hv was obtained irrespective of the amino acid type. This investigation revealed that, for the codeposition mechanism with arginine, the arginine was decomposed. The codeposited C was present in an atomic state in the film.

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Effects of azo-metal complex dyes on properties such as lightness value were investigated to examine a black thin organic coating (1-2 μm) on galvanized steel sheet for electrical appliances. This product consists of chromate coating and black thin organic coating on an electrogalvanized steel sheet or a Zn-Ni alloy plated steel sheet.
(1) Solvent azo-metal complex dye, solvent azo dye, carbon black pigment, and aniline black pigment were surveyed. The L-values of the thin coatings containing solvent azo-metal complex dye with 30-40 wt% content were less than 15, whereas the L-value of coatings containing carbon black pigment were more than 23. The dye was considered to be solved uniformly, although carbon black pigment aggregated in the thin coatings. (2)The weathering resistance of the coating containing azo-metal complex dyes was superior to that of coatings containing azo dyes. (3)The black thin coating containing azo-metal complex dyes can provide both good corrosion resistance and spot weldability. (4) Results demonstrate that the black thin organic coating (1-2 μm), consisting of azo-metal complex dye and organic resin, can provide a good black appearance, weathering resistance, corrosion resistance, and spot weldability.

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