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

• Published in: Materials and corrosion 2017-07, Vol.68 (7), p.791-798
• Main Authors: Peng, H.‐T., Che, C.‐S., Kong, G.
• Format: Article
• Language: English
• Subjects: alloy; Alloying additive; Copper; corrosion; Corrosion effects; Corrosion products; Corrosion resistant alloys; Electrochemical impedance spectroscopy; Open circuit voltage; Phase transitions; Polarization; Scanning electron microscopy; Surface properties; tin; Tin base alloys; X-ray diffraction; Zinc
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.201609313

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. The microstructure and corrosion behavior of Sn‐Zn alloys containing Cu utilized as touch‐up solders to zinc coating have been studied. It can be found that the addition of Cu to Sn‐50Zn alloys had not only refined the microstructure but decreased the corrosion paths resulting in improvement of corrosion resistance of the Sn‐50Zn alloy.