How to seal air tank leaks from inside

[yellowcake]

I had a rear bumper fabed by an expert welding friend that was constructed to function as an air tank as well. Although the bumber itself turned out increadible, and the welds appeared flawless, but under a low pressure test they leaked micro bubbles from invisible holes on the welds. He tried to fix them, but there are too many and they are so small that we thought we could seal them using some high tech version of green slime or bars leaks. Any ideas on how I might seal the tank by blowing something inside? I was thinking of a gas tank liner type rubberized compound but not sure.

Thanks

 

[bikersmurf]

Aviation fuel tank liner should take care of small leaks. Pour in, slosh around, pour out excess.

Never used it myself, but know it works for pin leaks in gas tanks.

 

[fieldsken1]

Just take the time and finish welding the holes. If you use some kind of product that says it seals holes it might fail when you need it most

 

[61n72cruisers]

sounds like there were contaminates in the material(s) when it was built...
what kinds or rods did he use to weld it? if the pipe was dirty, scaled, rusty, etc, #6011 would probably work best. if the pipe was in that condition and he used a 7018 rod, then the welds WILL leak!
you should probably just grind down all of the leaky welds, thoroughly clean the surfaces and reweld it.
oh, and btw, it's almost impossible to patch pitting, small holes in welds by just welding over the pits; you have to grind the weld down to the bone!

 

[Pin_Head]

I had the same problem, but it really doesn't matter. They are so small that the compressor doesn't notice.

 

[BEE-JAY42]

What you've got is a pressure vessel with welds that aren't up to scratch, I wouldn't be using it myself.

 

[yellowcake]

Rewelding is not really an option at this point since its already painted and mounted, but like Pinhead mentions, the compressor probably wont even notice, and if nothing else, at least I have a built in pressure relief!.
Thanks

 

[chevurai]

Pressure relif=Boom!

 

[Steamer]

How bout a picture.

 

[BEE-JAY42]

Two years ago a week before Christmas we had a driver helping to change a tyre on a trailer, it had a side wall failure when it was lower off the jack and blow out, I helped clean what was left of him from the workshop floor, the tyre had 90 PSI in it, he left behind a wife and two young kids. But the choice is yours.

 

[fieldsken1]

Do it again and learn from it. I know I have done things a second time to get it right.