We are a producer of Copper air conditioning components and brazed assemblies. Due to the high price of Copper, there has been a recent push to break into the Aluminum market. There are many concerns we are currently addressing, the most concerning being the conception that joining Aluminum and Copper is a very risky proposition. I have successfully joined Aluminum to Copper as well as Aluminum to Brass using a Zn-Al alloy with favorable leak testing results.
However, when placed in salt water, with a charge from a 9V battery, the braze alloy broke down creating a void in the braze material. Even more concerning was the deterioration of the brazed material in Alum/Alum braze joints.
My question is: is there anyone out there who is routinely joining Aluminum and Copper and would they be willing to share some expertise?
Thank you
I don't have the experience You need, but I will mention that placing aluminum & copper or brass in an electrolite will crerate a galvanic cell and cause corosion problems. The less noble material [aluminum] will be lost. In the case of the Zn-Al solder You mentioned, the solder, due to it's zink content is the least noble.
By 99205 
Date 02-07-2011 08:25
Edited 02-07-2011 08:39
Zn is a sacrificial anode in the marine environment applications so it would make sense the ZN in the solder would deteriorate when tested in the manner you put forward. This may be a situation for Brazing. From what I understand soldering/brazing copper to aluminum is not recommended if you want any type of longevity in the connection. Use steel transition piece between aluminum and copper. Coat one steel end with aluminum. Braze coated steel to aluminum with Al 4047. Braze uncoated end to copper with Aufhauser Silver brazing alloy A-45T. Looks like productions cost increase compared to the continued use of copper/copper connection needs to be looked into.
I really hope you give it careful consideration.
I just had a $1000 evaporater repair bill on my Carrier home AC due to corrosion. The word on the web is that they went to a Mexican vendor that did not properly clean the flux. I am now wondering otherwise. I had small perforations that allowed minute freon to leak out over a long period of time. In my case the unit lasted 5 years and one month - just a month past warranty. In other cases, people are getting just 1.5 years out of the units. One guy on the web has gone through 3 units already on a 5 year old system in a new house. There is plenty of moisture to aggravate the problem too...
