In article , mm wrote:

So I had some dirty pennies, plus one each of a nickel, dime, and
quarter, that were dark or had white or even blue stuff on them. Some
had been sitting in water somewhere maybe.

And following the dictum, google is your friend, I didn't ask here
what to do, but looked it up How to clean dirty pennies, dimes.

And it said use vinegar and salt, and I did, and the worst ones look
better now, but the rest of them look worse!! They all have white
"powder" stuck to them, and it doesn't come off. So I rinsed them in
water again (even though I'd rinsed them plenty after the vinegar.)

BTW, none of the pennies came out shiny, like the web pages said it
would

Is it because I didn't use white vinegar? I used cider vinegar.
Surely that's okay. Not enough salt.

What should I do now? Can I take them to the bank and then it will be
the bank's problem? What about the mint? Don't I owe society more
than that?

I'm going to buy some Cherry Zero Coke tomorrow. Will that help? Do
I have to omit the Cherry? (I remember that diet works as well as
with sugar)

Post-1982 USA pennies and some 1982 ones are copper-clad zinc. Older
ones are solid copper alloy. The older ones can be cleaned with many
acids, but in my experience never come out shiny like brand new ones.
Instead, they come out copper-colored but dull.

As for copper clad zinc ones? Since I last tried this before 1982, I
don't know. But I imagine the cheaper composition does not do as well.
And if any copper clad zinc pennies have scratches through their copper
claddings into the zinc, then your cleaning agent will reach the zinc.
Most acids corrode zinc.
--
- Don Klipstein )