Nope a oil drum is not a pressure vessel, 50-60psi and you will possibly explode it as the top and bottom are pinched together not welded. You need something that will take 1.5 time as much pressure as what the tank will hold at normal operating pressure (ie. 100psi operating= 150lbs tested pressure).

if you want something a little different maybe go to your local brewery and see if they have any kegs they are getting rid of. take it to a welding shop that does pressure vessels and have them weld a fitting to the top for the air lines. they can test it as well.