So it's not just me then. The dealer resprayed the NS doors and sills before I bought it. I then got the OS doors and sills sprayed after. It's been fine while in my care though - well, a few chips but nothing like what the previous owner did to it in fewer miles. It was in Scotland though.
The galvanising is just a coat, like any paint I suppose. A deep scratch will go through it.
The NS paintwork is now going dull. As I said though, my Croma's just a workhorse. It gets a good wash and a hoover and polish inside every now and then, plus a wax every 6 months or so. With my paintwork it wouldn't be worth trying to make it look good, so it's a good excuse to not care about it.
I did do some chip-filling and smoothing on the bonnet after I got it, and I was quite surprised how thin the clear lacquer is - a couple of rubs and you're through it. I'm not an expert though, but I'm sure it was a fair bit thicker on my previous Kia.