What Type of Solder is Lead Free and Remains Bright and Silvery after Cleaning?

by Thomas Edwin.

What type of solder could I use that is 100% lead free and will remain bright and silvery after cleaning with citric acid?

I plan on building a copper shotgun condenser for alcohol purification.

After I solder the copper parts together I clean the entire piece in a concentrated solution of citric acid.

It cleans the copper very good but the solder joints gets a grayish black residue on it that has to be removed with a wire brush.

Even after wire brushing with time it becomes tarnished and dull.

I’m looking for a solder that stays clean and shiny after cleaning.

Thank you.

Thomas Edwin