When deciding whether to use gas metal arc welding or flux cored arc welding for your application you must consider three variables: what you are welding, where you are welding, and the surface finish requirements for what you are welding.

• GMAW uses a continuous solid wire electrode for filler metal and an externally supplied gas, typically from a high-pressure cylinder, for shielding.
• The wire usually is mild steel, which typically is copper-colored because it's electroplated with a thin layer of copper to protect it from rusting, improve electrical conductivity, increase contact tip life, and improve arc performance.
• The shielding gas, usually carbon dioxide or a mixture of carbon dioxide and argon, protects the molten metal from reacting with the atmosphere. Shielding gas flows through the gun and cable assembly and out the gun nozzle with the welding wire to shield and protect the molten weld pool.
• If exposed, molten metal reacts with oxygen, nitrogen, and hydrogen in the atmosphere. The inert gas usually continues to flow for some time after welding to protect the metal as it cools. A slight breeze can blow the shielding away and cause porosity in the weld, so you should avoid welding outdoors unless you erect special windscreens.
• If done properly, GMAW can yield excellent results. The finished weld has no slag and almost no spatter. If the material you're welding is dirty, rusty, or painted, you must clean it by grinding until you see shiny, bare metal. A novice can use GMAW successfully with common commercial metals — low-carbon steel, low-alloy steel, stainless steel, and aluminum