Purge dams seal two sides of a pipe on each side of a weld to create an area that can be filled with purge gas before welding. Paper purge dams are preformed to fit a specific size pipe, making set up quicker than purge paper that has to be cut to size and fit for each application. Purge dams can be placed closer to the weld seam than purge bladders, which reduces the amount of gas required to fill the weld pool. Purge gas is an inert gas that improves weld quality and ensures the metal's corrosion resistance is not compromised. Pipe purging is done before TIG welding stainless steel, aluminum, and other corrosion-resistant materials to prevent oxidation that can negatively affect appearance and the material's corrosion resistance.