MIG.TIG-Both are argon welding as both the processes uses argon for shielding as it is a innert gas. (Inert gas - Used to shield the electric arc from outside contaminants and gases which may react with the weld. An inert chemical is one with a full outer shell of electrons which do not normally react with other substances. Inert gases include argon and helium. Some other non-inert gases are used for welding such as CO2. ) -MIG stands for Metal Inert Gas welding, many times called Wire-feed.. Also referred as GMAW (Gas Metal Arc Welding). The "Metal" refers to the wire which is what is used to start the arc. It is shielded by inert gas and the feeding wire also acts as the filler rod. A semi-automatic process, it is fairly easy to learn and use. -TIG stands for Tungsten Inert Gas welding. Also called GTAW (Gas Tungsten Arc Welding) and Heliarc庐 which was Linde's trade name for the TIG process when it was introduced many years ago. The arc is started with a tungsten electrode shielded by inert gas and filler rod is fed into the weld puddle separately. A slower process than MIG, it produces a more precise weld and can be used at lower amperages for thinner metal and can be used on exotic metals. TIG does require quite a bit more time than MIG to learn. It is similar in technique to gas welding.