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Heat exchanger pipe welding


I am an experienced welder but recently ran onto a couple of new things to me.

A heat exchanger pipe from a local dive boat. I cleaned off the corrosion and found the extent of the crack which extended from the square mounting flange about an inch and a half longitudinally along the pipe. I tried initially to TIG this crack using si-bro filler rod and dcen. But I got immediate burn through as the pipe was very thin from electrolysis, a lot of hissing and fumes. I backed off. Contacted a friend of mine who ran a radiator shop for 15 years and we cut a piece of copper plate and soldered it into place to cover the crack.

This pipe appeared to be brass or some alloy of copper.I was concerned about the excessive hissing, etc. Any ideas if this material is weldable and how? Perhaps a/c instead of dcen? I could not afford to play with this as it was an only piece and it was an emergency repair. No second chances here.

I have also run into some conflicting information on welding bronze. Seems as though some folks us dcen and others prefer a/c. What I have is a bronze strut. The part of a vessel that holds the propeller shaft in a straight line after it exits the hull of the vessel. The strut has a horizontal crack in it and will continue to crack if not repaired.

Grinding out the crack to bevel it out is generally the first step here as with many crack repairs. But I have never welded on bronze.
I bought si-bro rod from the local weld supply store for this job.
Maybe you could enlighten this old dog a little about this repair and the proper weld procedure.
Thanks. Doug


You sound like you have been around the block a few times.

The hissing sounds like you might need to make sure you have a vent somewhere so pressure doesnt build on you and hiss and mess up your weld.

Corrosion is a problem. if the thing is full of stress corrosion cracks, it aint gonna work and you probably did the best thing in soldering a doubler.

The strut may be nibral bronze...a popular marine alloy.
AC or DC works. you are right that it seems conflicting, but AC flows cleaner and wets easier, dc pinpoints a little better but welds a little dull and if there is any aluminum in the bronze DC will not work as well.

Helium mixed with the argon helps too.

There is a web site that offers pretty good information on welding propellers and stuff.

here is the page with propeller and skeg welding

good luck


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