A pretreatment with galvanostatic etching for copper electrodeposition on pure magnesium and magnesium alloys in an alkaline copper-sulfate bath

摘要

A pretreatment with galvanostatic etching is recommended to obtain an adherent and uniformly covered copper deposit on pure magnesium and magnesium alloy specimens (AZ31 and AZ61) in an alkaline copper-sulfate bath. The effect of galvanostatic etching on the surfaces of Mg and Mg alloy specimens can be realized by their potential variation during galvanostatic etching, in which four distinct stages could be distinguished. Galvanostatic etching to stage III, an activated surface of Mg or Mg alloy, was obtained for electroplating a uniformly covered Cu deposit in the alkaline Cu-sulfate bath. The Cu-deposited Mg or Mg alloy was used as the substrate for further Cu and then Ni electrodeposition in acid plating baths to obtain a protective Ni/Cu coating. The proposed electroplating baths are environmentally friendly, and the electrodeposition process is easy to conduct to achieve a protective coating for Mg and Mg alloys.