Purge bladders fill with air to 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. Purge gas is an inert gas that improves weld quality and ensures the metal's corrosion resistance is not compromised. Purge bladders are reusable. 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.