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Parkerizing / Phosphating of gun parts


Q. Dear Sir,

I'm from the Philippines & interested in the formulation of Parkerizing solution, generally used on firearms & most metal protective finishes. Currently, I'm into restoration of old motorcycles, especially Antique Harley Davidsons. Since most suppliers of "Parkerizing solutions" in U.S. cannot ship their products, I would just formulate my own and maybe introduce it to other gunsmiths & restorers as well. It's colors are usually grayish, greenish or black. They also call it Manganese phosphating. It would be a lot of help to have a do-it-yourself finishing solutions for us here.

Thank you very much & hope for your response.

Conrad Peralejo
- Quezon City, Philippines

Parkerizing Solution

Gun parts & schematics at Brownell's



You need a number of things to do a "home-brew" "Parker-job", but only 4 ingredients.

1. Phosphoric Acid (the active ingredient in Naval Jelly [linked by editor to product info at Amazon]) usually procured at a chemical supply house.
2. Powdered Manganese Dioxide (a very dense and heavy dark gray to black powder) also available at any chemical supply house.
3. Distilled water (I've used tap water, but the distilled stuff gives more consistent results).
4. A biscuit of steel wool [linked by editor to product info at Rockler] (don't use soap pads or Brillo pads!)

I used to do this on the kitchen stove (I wasn't married in those days) in a one gallon Pyrex beaker (these little beasts are expensive, so be careful with them). Metal pots don't work as well (if at all) I understand, but then I never used anything else but Pyrex.

Proceed as follows:

1. Use one whiskey jigger (yeah, this is really scientific, right?) of phosphoric acid added to the water. Remember your high school chemistry, ALWAYS add the acid to the water, and it is best done by pouring it down a glass rod!

2. Use one whiskey jigger of the (powdered) Manganese Dioxide in the solution.

3. Bring the solution to an extremely slooowwww rolling boil .

4. Now add your biscuit of steel wool.

I used wooden sticks placed across the top of the beaker and suspended the parts in the solution using steel or iron "machinist's wire or some such. DON'T use painted coat hangers or any wire with grease on it! You can usually get this stuff from a machine shop or from Brownells [linked by editor to Brownells website].

The parts should be totally immersed in the solution, being careful that anywhere the wire touches the part won't show on the finished part (usually easy to do -- like in the firing pin hole of a bolt). The part(s) to be Parkerized should be totally "de-greased" and sand or bead blasted prior to finishing (depending on the texture you desire on the finished part). Once you have bead blasted the part, you should handle the part with gloves (never greasy hands) and store them wrapped in clean paper towels awaiting the Parker Bath. Any grease on the parts or wire will cause what can only be politely called a variation in color (the parts come out streaked and spotted like a "paint horse").

I usually let the part remain in the solution for a total of 20 minutes (less MAY work, but I was told 20 minutes so that's what I used and it worked marvelously). When you withdraw the part, immediately rinse it in hot running water to get the solution off of it. Use extremely hot water, and the part will dry itself. Let it dry (and get cool enough to touch) on some clean paper towels, spray on some lubricant and voilà you are done!

Rumor control said that if you immersed the freshly rinsed and still hot part in Cosmoline, it would give the sometimes sought after "gray-green" tint to it. I have never tried it.

The original formula called for Iron Filings [linked by editor to product info at Amazon] vs. steel wool, but since I didn't have any floating around, and didn't want to file on the cast iron stove, I found that the steel wool worked just fine. What you get is a chemical reaction that causes an iron phosphate to form on the metal (steel phosphate I suppose, using steel wool). I have found that the resultant finish is just as durable as the Arsenal finishes and has exactly the same appearance! -- an attractive dark gray, almost black. Some say that adding more manganese dioxide causes a darker finish, but I've never tried it, as I was happy with what I got!

We often used this technique when finishing .45s built on early Essex frames that needed a lot of fitting, thus often requiring the removal of offending metal. I used to checker the front straps (also violating the finish in a rather spectacular fashion) and the resultant finish worked great and showed little or no wear even with extensive use -- much like the official GI finish. I'm still using a wadcutter gun I performed the magic on back in the '70s and it still looks new.

A couple of cautions:

1. Always be careful of any sort of acid, even such an innocuous acid as phosphoric. I certainly would never deliberately inhale the fumes (although there is no great odor to the process that I could tell, but then I smoke cigars). I started doing this back in the early to mid '70s and still have no "twitch" that I can directly attribute to Parkerizing on the kitchen stove. Just use common sense, WEAR GLOVES AND EYE PROTECTION ANYTIME YOU ARE PLAYING AROUND WITH BOILING SOLUTIONS (with or without acids being involved).

2. Be very careful not to cause any splashes with the boiling solution (of course the same can be said of boiling corn).

3. Prepare your area and your parts before hand, don't try to do this on the spur of the moment.

4. Once you have allowed the solution to cool, you are DONE! Re-heating it don't cut it, It simply doesn't work (I've tried it on several occasions). Have everything that you want to Parkerize ready to go when you fire up the solution. You can keep Parkerizing as long as the solution is hot, but allowing it to get cold kills it -- you've gotta brew up a new solution and start from scratch.

Dave Ruggs


A. You are using a one gallon container to submerge the items in. Use slightly less than one gallon and it won't boil over when you add the items, slowly, to the roiling solution.

Vincent Tracey
- Manhattan, Kansas

Q. How much water to one jigger of acid? Thanks. Rick

Rick Yuke
- Moose Jaw, Saskatchewan, Canada

April 12, 2009

A. One doesn't have to use pyrex containers for parkerizing. Steel containers work just as well. I use a long mild steel tray for parkerizing barrels. Works fine.
DO NOT TRY STAINLESS containers, they will interfere with the parkerizing process, and leave small little "speckles" on your finish.

Q. When parkerizing rifle barrels, is it necessary to plug both ends of the barrel before parkerizing it? If so, how?


Mike Kelly
- Wagener, South Carolina

December 28, 2009

Q. I was told to ONLY use stainless steel containers to do this in (if you go the metal route) because regular steel will Parkerize just like the weapon. Before I go out and purchase a very expensive stainless steel tray, can anyone confirm that stainless steel is/is not the way to go? Thanks.

Mark Quimby
- Birmingham, Alabama

September 26, 2010

A. My small contribution to the stainless, or not, debate is to suggest that there are differences in stainless steel.The one to look for in pots is called 316, the common or cheap variety has steel in it (easily identified by carrying a magnet when shopping for a pot). The steel content would account for spotting. Strangely whilst looking for a pot I discovered that some cheap Chinese pots are 316. Hope this helps.

Peter Fleming
- Hobart Tasmania Australia

December 1, 2011

A. The speckles from stainless steel is chromium or nickel dissolved in the acid that makes up a main part of the SS alloy. Pyrex is the way to go. All steels are going to leave behind some of their alloy content in the acids, even 400 series stainless. (300^400 series SS is magnetic, 400^300 is not)

For sealing the two ends...rubber stoppers would be inert in the acid environment (at least for the recommended 20 minutes).

Antonio DiNunno
- Pittsburgh, Pennsylvania

A. Thanks, Antonio. We've corrected your typo about the magnetic characteristics of stainless steel grades.

Decades ago I was involved in designing/building many huge zinc and manganese phosphating lines for General Motors and Caterpillar. 316L stainless steel is the ideal way to go if you can afford it.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

April 1, 2013

Q. I have recently been trying my hand at Manganese Phosphate and Zinc Phosphate treatments for gun parts.

The formula I'm using for this is:

Manganese Phosphate
4 oz Jasco Prep and Prime (75% Phosphoric Acid)
2 oz Manganese Dioxide
1 Gallon water
1/2 Biscuit De-oiled 000 Steel wool
190 °F
Immerse Lightly Sandblasted and cleaned parts for 8 minutes
Parts come out nice and Dark charcoal grey (almost black)

Zinc Phosphate
4 oz Jasco Prep and Prime (75% Phosphoric Acid)
8 Zinc pennies dissolved (It's all I had)
1 Gallon water
1/2 Biscuit De-oiled 000 Steel wool
190 °F
Immerse Lightly Sandblasted and cleaned parts for 8 min
Oddly, Parts come out nice and Dark charcoal grey (almost black).. Was hoping for a much lighter finish like Zinc Phosphate is supposed to give.

1. Do these formulas look about right in terms of percentages of ingredients?
2. Should I be using the Steel wool in both solutions (is that why my zinc solution is making parts black)?
3. I have heard of using Nickel Acetate to improve the finish. I happen to have some around as I use it for sealer for anodizing. If it is applicable, how much should I use based on the batch sizes shown?
4. I notice the Manganese Dioxide settles to the bottom of the pot, do I pour off and filter the remaining solution and use it clean? Or should I just stir up the pot and keep it suspended while processing my parts?

Thanks a bunch for any information, tips or suggestions.


Richard Dubey
- Torrington, Connecticut

April 8, 2013


1. Do these formulas look about right?
- They look very close to some of the other formulas I've seen for parkerizing.

2. Black parts from Zn3(PO4)2 bath
- My best guess is that you're ending up with a black zinc and copper oxide layer. The extra stuff in the pennies is probably where your problem is coming from. Start with pure zinc. The steel wool might be causing a problem depending on the impurities in it. It's the only other unknown in the solution besides the pennies that I can see.

3. Nickel Acetate
- I have no idea, I suggest doing some small batch testing. Go up in increments of 3-5 g/ml and see what works best for you.

4. Manganese Dioxide
- If it's precipitated out I'd think that it's not doing much for the chemistry of the bath, filter it out and set aside. Test the bath and see if you have a better finish, if not replace and agitate.

Marc Banks
Blacksmith - Boone, North Carolina, USA

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