Tin-manganese alloy electrodeposits I. Electrodeposition and microstructural characterization

The electrodeposition of tin-manganese alloys from aqueous solutions has been proven to be extremely difficult and only limited success has been achieved in the past. In this study, silvery matte and adherent tin-manganese alloys were electrodeposited from a modified sulfate/gluconate electrolyte within a current density range of 1-4 A/dm(2) at room temperature. The cathode current efficiency was generally greater than 50%, which is relatively high for the deposition of manganese alloys. The manganese content in the deposits varied with the applied current density from zero to a maximum of similar to 40 wt %. No oxygen was detected in the deposits. The result of X-ray diffraction analysis indicated that tin-manganese alloys deposited at 1 A/dm(2) mainly consisted of fine-grained MnSn2, while alloys deposited at higher current densities were close to amorphous. The successful electrodeposition was attributed to the five-fold (minimum) increase in the concentration of tin(II) ions in the electrolyte compared to that reported in the literature, and the addition of a non-ionic surfactant, Tween 20, which suppressed the preferential deposition of tin, thus enabling the co-deposition of manganese. While the electrodeposition process was successful, the deposits were prone to rapid and spontaneous growth of tin whiskers during storage. (c) 2006 The Electrochemical Society.