The Hakko FS-100 paste re-tins oxidized soldering iron tips and is 100% Lead-Free. The flux does not contain Diammonium phosphate and does not leave a corrosive residue. (Conforms to JIS-Z-3197 6.6.1 test method.) Depending on the severity of the oxidation and/or corrosion, the FS-100 will help rejuvenate very oxidized and/or corroded soldering iron tips back to useful life. Cleaning procedure: Oxidized tip: Re-tinned: For optimum performance, use the FS-100 paste in conjunction with the Hakko FT-700 tip polisher for increased oxide removal. 1. The suitable temperature for cleaning is around 350℃. 2. Tin the tip with the chemical paste FS-100 (to remove oxides). 3. Wipe out the chemical paste FS-100 left on the tip with a cleaning sponge or cleaning wire. 4. Feed solder to the tip and see whether or not solder wets on it. 5. Repeat the above steps of 2 to 4 until solder wets on the tip surface. 6. If solder wets on the tip surface again, feed enough solder to cover the tip to prevent oxidation at the end. Reference: Usage Guide