Ultrasonic method for removing heavy corrosion?

[deepsecrets]

Harbor Freight has a cheap ultrasonic cleaner for $27 on sale - anyone have comments on how effective ultrasonic methods are for removing heavy corrosion on coppers?

 

[OWK]

I have learned from experience, that removing heavy corrosion on coppers is a bad thing.

If the coin is heavily pitted, cleaning it will destroy all detail.

You're better off lightly toothbrushing off the surface dirt, and leaving what detail the coin has.

 

[maipenrai]

Ultra Sound didnt work for me, although after buying a new ring, and getting it cleaned every now and then, it seems to work well.