Flux Core Arc Welding is an electric arc welding process where a welding gun constantly feeds a hollow wire electrode into a weld joint. The hollow wire is filled with flux, a chemical composition that protects the metal, helps to fuse the two metals together and removes metal oxides to prevent rust. Flux Core is similar to MIG welding and can be automatic or semi-automatic, however is does not require an external shielding gas, like carbon dioxide or argon. Instead, the flux forms a coating around the weld allowing it to cool more slowly and create a more secure weld. This type of welding does create a slag that sits on top of the finished weld that must be chipped off.

Flux Core welding is used on pipeline welding, underwater welding, ship building and manufacturing. The flux contained in the electrode also allows the process to be more forgiving of base metal that is somewhat rusty, dirty or otherwise contaminated.