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Effect of trace Mn modification on the microstructure and corrosion behavior of Sn−9Zn solder alloy

The effect of trace Mn modification (0.05–0.1 wt%) on the microstructure and corrosion behavior of Sn–9Zn solder alloy in 0.5 M NaCl solution (pH 5.8) was evaluated by electrochemical techniques complemented with surface characterization. Mn could refine the Zn‐rich precipitates and facilitate forming of a new ternary precipitation phase containing higher amount of Mn element. Impedance results reveal that trace Mn modification improves the corrosion resistance of Sn–9Zn alloy in the solution. As a result, both cathodic and anodic reaction rates were reduced. Moreover, Mn notably enhances the stability of the passive films formed on the modified alloys with respect to a lower passive current density to maintain the passive state. Mott–Schottky analysis shows that the passive films exhibit n‐type semiconducting properties and the donor density decreases with Mn addition. The mechanism by which Mn influences the corrosion resistance of Sn–9Zn alloy can be explained in terms of the differences in both microstructure of the alloy and in semiconducting properties of the passive films.

Mn refines the Zn‐rich precipitates and facilitates formation of new ternary phases. Trace Mn modification improves the corrosion resistance of Sn–9Zn alloy. Mn notably enhances the stability of the passive films formed on the modified alloys. The mechanism by which Mn influences the corrosion resistance is proposed.

Authors:   Jian‐Chun Liu, Gong Zhang
Journal:   Materials and Corrosion
Year:   2017
Pages:   n/a
DOI:   10.1002/maco.201709694
Publication date:   29-Dec-2017
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