Tank repair patch ..weld or braze

[paulincayman]

Happy New Year..
I'm refurbing my 3CL tank. I just removed a  small Allen bolt from the inside tunnel face ...r/h side .I had to grind it off. There was a copper washer on the outside and a plain nut on the inside. I'm assuming it was a plug for a pin prick hole , it never leaked all through the de rusting process. I hope it was not some super important  part. Anyway it's gone.
I have a patch ready to go on..question is will  bronze office or should I use some kind of ferrous rod and attempt a fusion weld. I'm thinking the tank has to be pretty thin at this point especially around the area to be patched, although it does lot pretty solid after some poking around.
I'm leaning towards bronze but would  appreciate an expert opinion.
Thanks
Paul

 

[Basketcase]

Braze/bronze gets brittle and cracks if subject to stress fatigue such as on thin mudguards. Work hardening of copper alloys.

Should be OK on unstressed panel and easier to work with.

 

[Chuck3CL]

I had complete success repairing rust holes some more than 5mm wide in my 3CL tank using silver solder and a small pinpoint gas flame. The flame kept the heat very localised, and the cleaned steel with flux took the silver well. Large gaps were done by building a solder bridge. I then used a 3 part tank sealer internally. No problems.

 

[CLEMTOG]

"Braze/bronze gets brittle and cracks if subject to stress fatigue such as on thin mudguards. Work hardening of copper alloys."

not absolutely correct.

you cannot butt weld with bronze/braze, call it whatever you like, a crack cannot be repaired this way, it could be overlapped/overlayed with a patch and silver soldered using a capillary process, but bronze/braze is a higher temperature and fusion takes place with very little capillary action.

In your case, cutting a larger hole and making a piece to fit it, would then be possible to but weld in place, TIG would be best for this, MIG could also do it, and so could Oxy acetylene, if you are a good enough operator. distortion would vary with those processes the last being the worst.

More rust will be evident than you imagine, here are some pictures of the tank from TOG which I am repairing currently.

Simon, post some pictures of your tank which "just had a pinhole or three"
CLEM

 

[Dellortoman]

That's not a repair Clem. That's a rebuild 

 

[paulincayman]

Thanks for all the replies, it is a nice round hole about 5mm with seemingly solid metal around it. I used the  25 x25mm patch  with silver solder and a small propane torch.  Looks very sturdy and I'm quite happy with it.
Leak testing overnight before final de-rust and oiling  inside prior to paint stripping.
Cheers
Paul

 

[stevepm2011]

Personally, I would cut a circular metal patch a few mm diameter bigger that the hole, and braze it in place.
Providing it fits closely, and the metal is clean, this is dead easy to do.