yea, its not solder, which you can de-solder, welding is permenant, it actually makes the pieces one, so you would have to cut, and weld, i think the cap idea is better, and be careful if you do patch the whole, don't get carried awaay with an angle grinder, it is real easy to make a tube paper thin in the attempt to make it nice and smooth, and then you have a big mess.
Grant J Farmer