Oatey #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. #5 paste flux provides great wetting properties for better solder flow and can be used with most soft solders. #5 paste flux complies with CA and VT lead content regulations.