Phosphate vs. Parkerized? [Archive] - Gunboard's Forums

: Phosphate vs. Parkerized?

01-04-2008, 10:05 PM
Sure a dumb question! Had thought Phosphate and parkerized were the same thing, but recently read a thread that claimed they were different. Can someone enlighten me on them?


01-04-2008, 10:08 PM

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Example of Parkerized .45 ACP ( semi-automatic pistol (

This article is about historical phosphating of firearms and military equipment. For modern phosphating, see Phosphate conversion coating ( For the wine term, see Robert M. Parker, Jr. (
Parkerizing (also called phosphating and phosphatizing) is a method of protecting a steel ( surface from corrosion ( and increasing its resistance to wear through the application of an electrochemical phosphate conversion coating (

So, maybe the distinction was between phosphating and phosphate conversion coating? One seems newer than the other, but seem to have almost the same end result.

01-04-2008, 11:00 PM
Sounds like the same thing to me.

Fushigi Ojisan
01-04-2008, 11:11 PM
A quick read through the history makes it sound as if they lost the Trademark (if they ever had one) to their name and Parkerizing became synonymous with phosphating. Much in the way "xerox" is synonymous with photocopying.

01-05-2008, 04:40 AM
Whatever the Germans did to later war k98's (called phosphated) looks different from what we now know to be parkerized.
Some of the German stuff looks almost like a clear/grey coating rather than a beadblasted darker/deeper grey.

01-05-2008, 04:51 AM
German phosphated finishes were usually NOT over a sand blasted surface, so the phosphate does not "coat" it as much. Phosphating etches the metal slightly, and retains oil. Over a roughened surface, the oil retention effect is enhanced.

Phosphating has several names. parkerising, Phosphating, and Bonderising are a few that come to mind. Cam shaft engineering places use "Phosphate 501" finish for example, whereas British military used "Bonderising", and US military "Parkerising"

01-05-2008, 05:21 AM
So if a "modern" park were done to (original surface finish, with no bead blasting) WWII bits that had been blued and then had the blue removed, then they would come out same same as original WWII phosphate bits?

01-05-2008, 07:57 AM
They are the same process, maybe different chemicals and prep. Phosphoric acid is the main ingridient. Parkerizing is a commercial label/term, via The Parker Chemical Company. If you can discover the long lost WW2 USGI 'green' park solution you'll be rich!

01-05-2008, 10:09 AM
The green park was not actually green when it was applied. The application of cosmoline turns the grey parkerized process a share of green over time.-especially after storage emerson in the goo for a few years. Phospate and parkerization are about the same thing with very similar properties and application prcoess. I beleive that the phospate process was done on finished metal-smooth and the parkerized process was done on bead blasted cleaned surface.

01-05-2008, 01:33 PM
Vic, cosmo may turn some park into a greenish shade, but application of solvent will turn it back. I've had several rifles (m1 and M1903a3) that were green in places the cosmo never went, or if it did would have been removed by solvent. Last I heard The Green was most likely a solution that may have been mixed incorrectly for some time, by accident, that may have contained too much nickel.
There used to be an M1 guy in NY who would green up your M1; he sprayed it with cosmo and told the owners to let it sit for months and dont touch it with solvent.

Bill In Indiana
01-05-2008, 04:18 PM
Parkerizing is a trade name for a phosphating process. Kind of in the same way Copy machines all make copies, but not all of them are "Xerox" machines.

Phosphating colors can be impacted by the chemicals used in the process, the mixture ratios of those chemicals, and by the length of time the solution has been used. The opacity, and color can also be impacted by the surface preperation IE: Bead/sand/vapor Blasting, acid dipping, etc etc.

12-14-2016, 04:47 PM
Parker used a particular prep, chemical and application protocol. To produce a phosphated finish. There are other protocols that result in a phosphate finish, as mentioned above. Colors and such will vary depending. Of course, a blue finish can also vary depending on exactly which process is used ...

mike radford
12-14-2016, 08:15 PM
Parkerization is a trade name for phosphate metal finish. Phosphate finishes can be Magnesium or Zinc based, thus influencing their color when finished. It has widely been traditional wisdom that the green US parkerized finish resulted from age and lube, not to mention that it was sandblasted and cleaned, then exposed to the solution for a set amount of time at a set temp. The US widely used a brown preservative oil. On pistols like the M1911A1 they were dipped in the solution, allowed to drip a while, then packaged. There is surviving video of this process. This oil tended to dry and look like brown fingernail polish in 50 plus years. The weapons stored with it on them tended to develop a green tint.

12-14-2016, 08:39 PM
I recall posts years ago that alleged the green color came from a depleted(weakened) Parkerizing solution and not so much from cosmo. But I have seen some real green cosmo on some arms.