Joining copper to aluminized ( exhaust pipe) steel

[Texasmark]

I put a coil of copper tube inside my stove water jacket and run a pump on the water heater to get unlimited hot water.
Good Luck !

You can do the same with your air conditioner high pressure line inside a roll of ¾ copper to heat your swimming pool recirculating pump water like a friend of mine did. Since the colder the lower the pressure and the lower the pressure for a given volume, the easier it is on the compressor and light bill, pays for the roll of copper quickly. Works great.

 

[tjflicek]

My guess is getting the right flux. Assume you are using a brass brazing rod. In the metal compatibility table I see that tin and steel are in the same group. I know that regular tin-lead solder adheres well to copper. Might try some 95/5 (tin/lead) "high temp" solder which I used in industry for high stress joints along with a good acid flux. I don't have the name handy, but my best acid flux is a white paste in a little white plastic jar, about 2" dia x 2" tall.

95/5 solder doesn't have any lead in its composition, it is tin and antimony. Its main use is as lead free solder for potable water piping, and as high strength joints as you said in hydronic heating and compressed air systems.

 

[Texasmark]

95/5 solder doesn't have any lead in its composition, it is tin and antimony. Its main use is as lead free solder for potable water piping, and as high strength joints as you said in hydronic heating and compressed air systems.

Ok, thanks for the clarification. Just assumed the 5% material as lead since most other solders are a mix of the two. Just googled the subject and you are right on. My usage was electronic circuits so I wasn't interested in the lead free, part.