Leaching behavior of tin from Sn–Fe alloys in sodium hydroxide solutions

The dissolution behavior of tin from pure tin and Sn–Fe alloys in sodium hydroxide solutions has been investigated using a rotating disc. The effects of the composition of the alloys, disc rotation speed, sodium hydroxide concentration, oxygen potential and temperature on the dissolution kinetics of tin have been studied. The dissolution rate of tin from a 50 wt.% Sn–50 wt.% FeSn2 mixture in sodium hydroxide solutions was found to be higher than that from pure tin. This is attributed to the fact that polarity reversal occurred between tin and iron from Sn–FeSn2 in sodium hydroxide media and therefore, tin of the FeSn2 acted as an anodic. The dissolution rate of tin from pure tin in sodium hydroxide solutions was found to be controlled by mass transfer of oxygen through the diffusion boundary layer. The dissolution of tin from Fe–Sn alloys, however, involved a mixed-control mechanism of diffusion and chemical reaction.