Effect of minor Cu addition on corrosion behavior of Sn‐Zn‐xCu touch‐up solder alloys

Abstract

The corrosion behavior of Sn‐50Zn‐xCu (x = 0, 1, 2 wt%) touch‐up solder alloys was investigated by electrochemical techniques (potentiodynamic polarization, electrochemical impedance spectroscopy, and open circuit potential) and surface characterization (scanning electron microscopy, energy dispersive X‐ray spectrometry, and X‐ray diffraction), aiming to explore the effects of the Cu addition on the corrosion resistance. The results reveal that the dendritic‐like Zn‐rich phase of Sn‐50Zn was disadvantageous to form a protective corrosion product layer and offered convenient paths for the Cl− penetration into the substrate. However, the Cu addition to Sn‐50Zn based alloys led to the refinement of microstructure and the transformation of Zn‐rich phase's morphology which could result in the formation of more compact corrosion product layer. Thus, the corrosion resistance of Sn‐Zn‐Cu alloys was improved. The corrosion mechanism is also discussed.