Steel, which has been treated by zinc-cyanide plating, is susceptible to hydrogen-embrittlement, though it is very powerful in rust prevention and throwing power or economically profitable. For this reason, it is difficult to be applied to thin spring material in practice.
In order to solve the problem, eight kinds of baths, containing Zn(CN)
258.7g/
l, NaCN 24.5-100g/
l, and NaOH 35.0-160g/
l were selected to measure their hydrogen-embrittlement, throwing power, and current efficiency. Then, the effects of concentration of NaCN or NaOH and electrolytic conditions on the above three factors in plating of high tension steels such as SK-5 were investigated.
The following results were obtained
1) The increase in NaOH content had good effects on throwing power, but no good on current efficiency and prevention of embrittlement.
2) NaCN content had little effects on current efficiency and throwing power. However, its content as low as 53g/
l among baths containing NaCN 24.5g/
l had good effects on prevention of embrittlement.
3) Low current density had good effects on current efficiency and throwing power. Whereas, considerably high current density had good effects on prevention of embrittlement.
4) The optimum temperature of baths for high throwing power was 25°C and high current emciency or preventive power of embrittlement was obtained at 40°C.
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