Mechanism for the development of Sn-Cu alloy coatings produced by pulsed current electrodeposition

• Published in: Materials letters 2018-04, Vol.217, p.120-123
• Main Authors: Wu, Liang, Graves, John E., Cobley, Andrew J.
• Format: Article
• Language: English
• Subjects: Alloys; Coated electrodes; Coatings; Copper; Copper base alloys; Electrodeposition; Intermetallic compounds; Materials science; Mechanism; Morphology; Pulsed current; Pulsed current techniques; Sn-Cu coatings
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2018.01.094

•Pulsed current electrodeposition results in a higher Cu content in Sn-Cu alloy coatings.•The mechanism for the development of Sn-Cu alloy coatings produced by pulsed current electrodeposition is proposed.•The mechanism is attributed to the occurrence of a spontaneous metal displacement reaction.•Sn-Cu coatings produced by pulsed current electrodeposition are composed of a dual layer of Sn-Cu and Cu6Sn5. Pulsed current (PC) electrodeposition has become an essential tool for producing coatings in a wide range of industries. The pulsed current can have a significant influence on the composition, morphology and properties of electrodeposited coatings and this is particularly true when plating an alloy. In this study, the mechanism for the development of Sn-Cu alloy coatings produced by PC electrodeposition was investigated. Sn-Cu alloy coatings produced by PC electrodeposition were essentially composed of a dual layer of Sn-Cu electrodeposits and Cu6Sn5 intermetallic compounds (IMCs). In addition, it was observed that pulsed Sn-Cu electrodeposits exhibited an increased Cu content. Experiments were carefully designed to elucidate the mechanism for this important finding and based on their results a theory is proposed which explains the increased Cu content in terms of a metal displacement reaction occurring during the ‘relaxation’ time of PC electrodeposition.