抄録
A study of electroless nickel-tin-phosphorus alloy plating from ammonia alkaline citrate bath (A-C bath) and from caustic alkaline citrate bath (C-C bath) containing sodium stannite has been made with reference to the effect of the tin content on deposition condition and the corrosion behavior of the alloy. It was found that the deposition rate increased with increasing amount of sodium stannite in A-C bath, but this effect was very small in C-C bath. The tin content in the deposits increased up to 19.2% in A-C bath and 12.4% in C-C bath. In a 0.5M sulfuric acid solution at 30°C, however, the tin cotent in the deposits from A-C bath increased about more than 7% and that from C-C bath increased more than 12%. Severe corrosion of the alloy in the solution is due to the formation of metastable phase Ni3Sn4. The corrosion resistance of the depeposits, containing 2.8% tin and 4.4% phosphorus, from A-C bath, and of the deposits containing 8.4% tin and 8.3% phosphorus, from C-C bath was excellent.
