It depends on the metal in the given coin also... if there is a lot of copper in it you wanna stay away from anything acidic.
If its a valuable coin any kind of cleaning with a chemical will damage its value but then if it was a dug coin its probably considered in poor condition already anyway
Vinegar and salt solution and run for 1/2 hr or so through tumbler or just put them in a can you can cover and shake every hour or so. Don't mix copper with clad or they will all turn green. Works great to get clean enough for coin machine
No Joke ,this is a Patent Item. I was getting ready for my 10 years Colonoscopy Exam and I had a Bottle of Magnesium Citrate ( Wally World--97 Cent ) I said if it works on Me why not try it on a (Greenie Beach ( Cent ) Coin )
Amazing Results in about 30 minutes, took the corosion off, Still need to try on other Coins ( Separately ) You Heard it 1st Hear - goldnugget-Charlotte,N.C. My S.C Club member's were astonished with the results.
If you're just talking about modern clad then it doesn't much matter just get them clean enough for the machine to take them and honestly they don't have to be all that clean for that to happen probably 50 percent of mine hardly get cleaned at all... Just dump them in the machine slowly so you don't jam it up.
If you're talking about coins that might have collector value then don't clean them