This inert atmosphere allows

MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding are the two most common forms of conventional seal. This works by using a shielding gas to create an inert atmosphere around the head.  the welds to be isolated from other gases in the surrounding area to stop the welds from becoming porous. An electric arc heats up the metal and metal filler, once melted it joins the material together to create a strong weld.