Kitchen sink scratches are NOT wear and tear, is it?

[Sam Leon]

I have an enameled cast iron kitchen sink at one of my rentals.  Never an issue for years, but this tenant moved in and I have never seen things abused to this level.  Handles of refrigerator yanked loose.  Kitchen hinges broke off.  Now my sink is all scratched up.  It's scratchless before they moved in.  This is what it looks like now.

It's badly scratched up and I don't think it's fixable unless I coat it but once I do I have to do it every year like those old tubs.

They said it's nothing it's just "normal wear and tear".  Do you think this is wear and tear?  If not how would you charge/deduct damages like this?