Reverse washing soda buildup on stainless steel In a home brewing project, I use washing soda (Na2CO3) to remove labels and glue from previously used bottles. In doing this, my flip-top bottles (which have a stainless steel flip top arm) often get unruly buildup of residual soda, which tarnishes and blemishes the steel. Is there a chemical mixture I can use to reverse this process and return the steel to a near-new appearance?

Here are a couple of photos of the bottles and buildup: the left shows a typical amount of residue; the right shows my attempt to wipe it clean with white vinegar (which partially works, but is still blemished).
If you use tap-water together with Sodiumcarbonate, chances are that the residue is Calciumcarbonate (unless your tap-water is very soft).

Calciumcarbonate is significantly less soluble in water, but can be dissolved in acid. I would try to put a bottle/arm in a hot 5% solution of acid (acetic acid is fine, personally I would prefer citric acid) to see if any (small) gas-bubbles are formed at the residues. If it does, it is carbonate and can be removed in an acid bath.

If not, the residues could be glue from the labels, and getting rid of this is probably more complicated.