manual metal arc welding is commonly referred to as simply arc welding arc welding is one of the most flexible and widely used welding methods arc welding does not use a shielding gas instead there is a layer of slag formed over the weld during the process this layer protects the weld while it cools as the current flows through the flux coated electrode the flux is what creates the layer of slag it forms an arc to the work piece and generates enough heat to melt the metal electrode and the work piece the two metals mix together to form a weld bead arc welding is noisy produces lots of sparks and smoke and the finished world needs to be scraped to get rid of the slag arc welding today is generally replaced by mig welding however for repairs and alterations outside like on buildings and bridges arc welding is still the preferred method if you're interested in welding or becoming an engineering apprentice call competence on oh 800 526 1 800 or visit competenz.org nz