working for one of the largest gas supply companies in the world, I have to say that if you did weld on this tank, it would be considered scrap. If you are renting or leasing this tank, you would be charged with loss of use on this cylinder. If you own this tank, you would now own a piece of scrap. it is very dangerous to weld on these tanks,and your supplier would not accept it at their site for refill or exchange.
'nuff said, i think.