This research examines the corrosion behavior of tin-zinc alloy electrodeposits on a steel substrate. These coatings were prepared using the commercial Dipsol SZ-242 plating solution. Previous research has shown that tin and zinc plate out as separate crystalline phases of nearly pure Sn and Zn in accord with the phase diagram. When potentiodynamic scans were run in a slightly acidic (pH 3.6) solution from open circuit potential (OCP) to more positive values, zinc was seen to preferentially dissolve from the Sn-Zn coating. Polarization tests were performed on the Sn-Zn coating to follow the changes in structure that occur as a function of the extent of zinc dissolution. Scanning electron microscopy (SEM), in conjunction with qualitative image analysis software, was used to obtain data that could be used to evaluate the role of the IR voltage in the corrosion mechanism associated with the selective dissolution of the zinc from the coating.
展开▼
