When I got my CZ 52 back in 1995 or 1996, it had a Parkerized phosphate finish. It was a really cool gray with a slight greenish cast. I really liked the look of it. My dad reminded me that Parkerization isn't the best rust preventative, and that I should oil it, so I did. The rag I used to apply the oil was surprisingly rusty looking on that first application. However, further applications in months and years to come showed that no more rust was coming from the phosphate finish.
The odd thing was that the pistol started to change color. The oil soaked into the phosphate, and after a couple of years the gray finish started to darken. Now the color is a very dark gray, almost black. The finish has gone from absolute non-gloss to a semi-gloss, perhaps because the oil polymerized with time and heat and oxygen. Oh, I haven't been using cheap oil on it either... it's synthetic and very resistant to oxydization. It's a very different look now.
Anyway, I figured you'd want to hear from someone else who had oil bring up rust. Keep oiling it, and you'll be just fine.
Scott
