Any rust protection from cold blue?

[tacotime]

I read once there is no rust prevention benefit from cold blue products once done, like the Birchwood Perma Blue.  True?
 
 

[Bigeasy]

For what it is worth, I once re-blued an old Mauser rifle barrel using cold blue, and it seemed to be more rust resistant then bare steel.  Lasted pretty well.  Key seemed to be heating the metal between coats.
 
Larry

[tacklebury]

I've cold blued a couple shotgun barrels.  It does help a bit and neither barrel has rusted more than a freckle by the spring release in 25 years or so.  I do keep a light coating of oil on my guns too though, so that probably has as much to do with it. 

[gunnut69]

Oxphoblue is a kind of chemical parkerizing and as such provides a surface that retains lubricant better than polished steel. So in that way it can provide some protection from rust.. the oxphoblues biggest asset is its ability to work through light oil and its wear resistance.. Some cold blues are little more than stains that darken the surface of the metal much like paint they require surface preperation and cleanliness... They don't wear well..