On Sat, 19 Jul 2008 19:26:43 +0100, Chewbacca wrote:

Used to work with a guy that had had a tiny drip of HF acid on his hand.
He had a hole about 4mm diameter and about 4mm deep in his hand. It
had been like that for 20 years. It never closed up....

That wouldn't have been HF, as that's almost invisible with skin contact
- one of the hazards of it. It's the calcium in bone that HF goes for.
There are plenty of other fluorine compounds that will produce super
long-lived ulcers though.