I've had my PF-9 for about 18 months now and carry it often. I have noticed some rusting occurring in the cocking serrations and along the very front of the slide. Can someone like LOKI coat HC? I would really like some sort of protection that doesn't rust at all. I mean it's not much but I'm a bit anal about rust.

I agree with gremlinmt.  I carry high % (like...all the time wherever I go) and oil my PK PF-9 with "Gunzilla" (best CLP ever!) regularly.  No rust whatsoever.  I do use holsters that provide a sweat protection barrier for the slide.  I live in FL so making sure the gun parts that need lube are indeed lubed is a must.  I check it every ~3-4 days and apply lube if necessary.  I thoroughly clean it and lube it after every range session, AT THE RANGE (you never know when you are going to need it, always be ready!).
 
But Loki's coatings will dramatically improve corrosion resistance on your gun.  I don't think is necessary if you tend to your gun regularly.
 
My .02

Like the poster above... Breakfree CLP on both my P3ATs and no rust [except, at first, on that spring pin at the bottom of the grip which I had not been paying attention to; remember to hit it also with CLP and no rust].
 
 
Bill K.

I'll have to try that Tuff stuff. I use miltec on most of my firearms but I don't want to carry an oily slide. I use miltec on the inside of course, but I guess I will have to go with a coating of some sort for better protection.
Pete, those small spots in the crevices are exactly what I am talking about! I try my best to scrape them with qtips until clean, then apply oil to them, just never seems to last .
 
thanks for all the answers