Plating on magnesium alloy die castings—the role of fluoride and pH

Influence of zincate pretreatment on adhesion strength of a copper electroplating layer on AZ91 D magnesium alloy

“…Huang et al [11] proposed a environment-friendly pretreatment with galvanostatic etching to obtain an adherent and uniformly covered copper deposit on pure Mg and Mg alloys of AZ31 and AZ61 in the alkaline Cu sulfate plating bath. Dennis et al [12,13] studied the effects of three proprietary pretreatment sequences, i.e., the Dow process, the Norsk-Hydro process and the WCM canning process on various Mg alloy diecasts, e.g. AZ91CC (Cold Chamber), AZ61CC, AZ91HC (Hot Chamber) and AZ71HC.…”

“…Generally, metal electroplating is performed by the following processes: surface cleaning, acid pickling, activation, zincating, and metal electrodeposition. However, highly toxic chromic acid has sometimes been used in the acid pickling process, and poisonous cyanide has also sometimes been used in Cu electrodeposition to improve the adhesion strength of Cu layer to the Mg alloy substrate [12][13][14]. Moreover, zincate pretreatment has been carried out at 70-80 °C, temperatures at which the composition of the zincate bath may change due to rapid water evaporation, resulting in low reproducibility of pretreatment for an Mg alloy.…”

Cold-spray coatings on magnesium and its alloys

“…The currently available surface treatment techniques for Mg alloys include electrochemical plating (Brown, 1994;Dennis, Wan, & Wake, 1985;Zhu, Li, & Shan, 2006), conversion coatings (Gonzalez-Nunez et al, 1995;Gonzalez-Nunez, Skeldon, Thompson, & Karimzadeh, 1999;Montemor, Simoes, & Carmezim, 2007;Rudd, Breslin, & Mansfeld, 2000), anodizing (Barton, 1998;Sharma, Uma Rani, & Giri, 1997) and organic coatings such as polymer-based paints (Mori, Hirahara, Oishi, & Kumagai, 2000). One of the major issues associated with electroplating is the use of toxic chemicals, such as chromium compounds, cyanide compounds and fluoride compounds, in both the pre-treatment and plating processes.…”

Surface Modification of AZ91 Magnesium Alloy

“…4 shows the surface morphologies obtained with or without sonication. It clearly shows a significantly higher surface coverage with the application of sonication, by comparing Figures 4(a It was suggested that in an Fcontaining aqueous solution, surface film containing Mg(OH) n F 2-n [6] may form and suppress anodic dissolution [7], thereby preventing the increase of copper coating coverage. Sonication is known for its capacity to erode/clean substrate surface mainly through asymmetric cavitation [8][9].…”