Soldering Galvanized Steel

I am trying to join two pieced of corrugated galvanized steel together to act as a solar water heater. One method I tried was to tin the low points of the galvanized steel before putting them together. I then put them together, clamped them, and heated them up with a torch to get the solder to melt which would then join the two sheets together. This worked pretty well, but it was not strong enough to hold 60 psi. The solder ripped off of the sheet metal at 30 psi. Besides applying more solder, what are some ways that I could increase the strength of the bond between the galvanized steel and the solder? What is the best type of solder and flux to use for galvanized steel? Your help would be much appreciated!

Hi, Tim. I'd like to hear suggestions myself! Meanwhile topic 15533 should be helpful.

My father was a plumber-roofer who soldered a lot of galvanized gutters and used to tell me when I was a kid that you can only do it with a solder bolt (those heavy old manually heated soldering irons), that you can't do it with a torch -- but I was too young to investigate whether there was any truth to it :-)

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey