Electrochemical behavior of a lead-free Sn–Cu solder alloy in NaCl solution

• Microstructure array and Cu content affect corrosion of Sn–Cu alloys.
• Microstructure has important role in current density and Cu content in electrochemical activity.
• IMC particles and cathode/anode area ratio have also effects on electrochemical behavior.

Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization techniques and an equivalent circuit analysis are used to evaluate the electrochemical corrosion behavior of Sn–Cu alloy samples in a naturally aerated 0.5 M NaCl solution at 25 °C. It has been found that a better electrochemical corrosion resistance is provided by a coarser cellular microstructure array. It has also been found that the corrosion current density (icorr) is of about a quarter when compared with that of the finest microstructure examined. Such behavior is attributed to both localized strains between the Sn-rich phase and intermetallic (IMC) particles and the cathode/anode area ratios. The effect of copper alloying on icorr is also discussed.

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