Oatey No. 5 Lead Free Paste Flux cleans and fluxes most commonly soldered metals including copper, brass, zinc, galvanized iron, lead and tin or copper-coated metals. Fluxing is a critical step in the soldering process. No. 5 Paste Flux provides superior wetting properties for better solder flow and can be used with most soft solders. No. 5 Paste Flux complies with CA & VT lead content regulations.