Properties of silver-tin alloy deposits from a pyrophosphate
bath have been studied to obtain data for using as functional deposits. Cathode current efficiency and the throwing power tended to decrease in current density. The highest value of the throwing power was obtained at pH 9, no pH effect on current efficiency being found. Satisfactory deposits were gained at the total metal concentration of 4.0 g I_ ' in the depositing bath, when tin eontcnt was 10 wt. y0 and hardness was Hv 186. The pH of depositing bath had a small effect on both composition and hardness of alloy deposits, however, the cfhect of cathode current density on them was remarkable. Increasing current density increased tin content of deposits and decreased hardness. The deposit of silver-tin (90/10) alloy had a different crystal structure from that of a metallurgical alloy and a smooth surface was obtained according to the SEM photographs. Then it was observed that alloying silver and tin minuted the crystal grain. This crystal fineness was found to mainly cause the increase of hardness.
With respect to the electrodeposition of the silver-tin alloy from a pyrophosphate bath, electrodeposits with various crystal structure can be obtained by the electrolytic condition. Further, current efficiency, surface condition and properties were found to be controlled by the crystal structure of eleetrodeposit.