Parkerizing always turn gray or greenish over time?

[RebelExtrm02]

Do all parkerized guns change color over time? I've seen many used guns (specifically mossberg 590a1 shotguns) in pictures and in gun stores that have a very light gray and sometimes greenish look to them.

I like my guns to be black and fear that if I buy a parkerized shotgun that it will turn light gray or green on me over time. Is there something that causes this specifically or any way to prevent it?

I've attached some examples of what I mean on the same model of shotgun new and used. Click to enlarge.

 

[Sam1911]

There are slightly different blends of parkerizing chemical solutions that create different color tones. Primarily these are the greenish-hued old military parkerizing like you see on vintage US GI guns (Garands, M1 Carbines, etc.) or the grey/black color more common on more modern arms. But they really don't change color over time.

However, the surface of a parkerized finish is microscopically porous. One of the great benefits of parkerizing is that it absorbs and holds oil. When you see a very grey-looking parked gun, it is often one that hasn't been oiled recently or has been stripped with gun-scrubber or similar degreaser. Oil it again and it will loom much darker, closer to black.

 

[Bubbles]

The light gray parkerizing is done with a zinc-based solution. If you then coat it in oil or cosmoline and let it sit for a while, the finish gets the greenish cast.

The dark black parkerizing is done with a manganese-based solution. It doesn't tend to go green or change color.

 

[RebelExtrm02]

Is it possible then that newer mossbergs are a different park than the older ones were? In person I've seen new parked A1's in the gun shops that were very dark gray but the used ones all have been either a very light gray or a light greenish gray.

I'm not really worried about the color of the gun, I just wanted to make sure that parkerizing didn't do any funny things over time.