MG Chemicals 4910 SAC305,  96.3% Tin, 0.7% Copper, 3% Silver, No Clean Lead Free Tip Tinner, 0.8 oz container
Tip Tinner is a mixture of solder powder and thermally stable, oxide-reducing compounds. Used to repair oxidized soldering tips for optimal performance and for extending the working life of new soldering tips. Use to clean and re-tin iron tips. While maintaining soldering iron at operating temperature, roll or wipe soldering iron tip over the surface of Tip Tinner for a few seconds until soldering tip is evenly tinned. Remaining residue after tinning can be readily removed by wiping with a wet sponge.