Parkerizing and Hydrogen Embrittlement

[ralfus]

The parkerizing solution temperature is 190 to 210 degrees for 40 minuets. That temperature and time will not affect the metalurgy of steel. Keep in mind that all the parts have been parkerized before.

Your still having a reaction at 40 minutes?

[Devil Dog]

I was just thinking of a maximum time somthing would stay in the solution. Most everything I do stays in 15 min. or so. I find bullet guides, safeties, sight covers and middle bands need a little extra time. My point is that parkerizing, wether it be the original or a re-parkerizing does nothing to the melalurgy of the part.

[mdoerner]

I was just thinking of a maximum time somthing would stay in the solution. Most everything I do stays in 15 min. or so. I find bullet guides, safeties, sight covers and middle bands need a little extra time. My point is that parkerizing, wether it be the original or a re-parkerizing does nothing to the melalurgy of the part.

Uhhh, that's why I asked the question originally, Parkerizing is a chemical process, can could change the heat treatment of the part if done improperly. You are dipping your parts into an acidic solution and depositing either Zinc or Manganese in it's place. So, yeah, it can screw up the metallurgy.

Danny has sent me an old gov't document on what should and should not be parkerized. I'll see if I can't put a link below for people to grab it. Basically, springs (leaf, torsional, and helical) and threaded rods/bolts should not be Parkerized as they do not have sufficient cross-section to withstand the hydrogen embrittlement causing failure.

http://members.cox.net/mdoerner1/MIL...s%20Metals.pdf

The file is 3.0 MBytes, so don't click the link if you have a pokey internet connection. Let me know if the link doesn't work.

After skiming thru it, Re-Parking a bolt a couple of times is OK, but I wouldn't want to do it 100 times or so. Springs and bolts (the threaded kind, not the Garand Bolt) are Parkerizing no-no's. Thanks again to Danny for emailing it to me.

Mike Doerner

[latigo 1]

I am not an expert on metal treatments but ran into hydrogen embrittlement problems a few years ago while building motorcycle race engines. Here is my understanding of it. Hydrogen embrittlement is the result of the acid baths that are commonly used when coatings or platings are applied to the part, as well as the electric current used in the process. Hydrogen is actually absorbed into the steel. I think it is usually only a problem on electroplated parts. The electroplating process locks the hydrogen into the parts and requires baking to release the hydrogen. Mechanical processes such as phosphating have a porous finish that lets the hydrogen escape on its own. Any plating shop in your area could probably give you a lot more scientific information, especially if they plate any type of high stress fasteners (bolts and screws etc.}

[John Kepler]

Parking isn't going to cause hydrogen embrittlement.....can't; wrong energy levels--wrong chemistry! You start worrying about it when you are dealing with electrolytic processes, and acidic treatments at fairly high temperature (salt-bath nitriding, etc.)...then you have to think about normalizing. Parking just isn't operating in the right energy realms for hydration to be an issue.

[Devil Dog]

I agree that parkerizing should not be done to springs and screws. Could the reason be, that parkerizing is a coating and will add material to these parts that may be affected by the extra material?

[mdoerner]

From the Mil-205A manual I posted in the link above........

4.1.2.1 Springs. Springs, primarily those having a small diameter, are apt
to become brittle during the phosphating process. This applies also to leaf
sprlngs and other parts of small cross section that takes spring loads.
Certain assemblies that contain springs which cannot be dissembled without
damaging the parts may be phosphated without disassembling.
Any springs which are phosphstized should be relieved of hydrogen
embrittlement by holding them at room temperature for 120 hours or heating
them for eight hours at temperatures of 210 to 220F (100 to 104C).

There you go. It CAN happen. Right chemisty, but Mr. Kepler is right on temperature (I'm making an educated guess here), I don't think it's high enough to screw up a Grand Bolt because of the thicker cross-section at the lugs. FWIW.

Mike Doerner

[mdoerner]

And again......

2.1.7 Acid pickling. Acid cleaning is not recommended as a method of
cleaning if any other method will remove the soils. When metal dissolves in
acid, atomic hydrogen is released and a portion of this is absorbed or
dissolved In the metal. Any resulting embrittlement of the metal, known as
hydrogen embrittlement,can result in breakage of steel under stress unless
the hydrogen is removed. Hydrogen removal is usually accomplished with heat.
The temperature and times required to remove the hydrogen absorbed during
pickling may also destroy the corrosion resistance of the phosphste coatings.
For this reason, pickling should never be employed before a phosphating
operation which is used to meet DOD-P-16232 without permission of the procuring
agency. The higher temperatures used in the black oxide treatments will
normally drive off the absorbed hydrogen from most hydrochloric acid pickles.
This acid is frequently used prior to black oxide treatments to remove all
traces of corrosion.

Granted, this is talking about using an acid to clean the metal before phsophating, but hydrogen embrittlement is still a REAL issue, even at the lower temps of the Zinc and Manganese Phosphating processes. It depends on the prep (bead blasting vs. chemical strip + sanding) and how soon the part will be used after the phosphating has been completed.

Yes, I'm kinda making H. Emb. a more serious issue than it need be. Many people have re-parked without issue and will continue to do so. But keep in mind, Garand bolts aren't being manufactured anymore and excessive re-parking of these components COULD cause premature failure of critical components (i.e. corrosion on the bolt lugs that are simply bead blasted, re-parked, and then immediately used, for instance.) But since the home brew kit I got from Palmetto, and the on-line instructions I've seen from Brownell's don't even mention it, makes me feel like it needs to be discussed. I'm not trying to state people shouldn't re-park without normalizing afterwards, but people gotta understand as these parts age, more stress cracks will appear over time and excessive re-parking could cause a failure whereas a shiny beat-up part may not fail (if you can call 60+ years after the parts were made premature failure)

Anyhoo, I've ranted a bit here. Time to get off the soap box....

Mike Doerner

[John Kepler]

Re: Springs:

Mike, you're forgetting that to make a spring, you have engaged in a phase-conversion that makes the metal MUCH more soluble to hydrogen. It's a special case, hence the warnings. As for the hydration in "acid pickling"....Mike, please check the specifications for pickling......it's done in a VERY low-pH environment and at temperatures much higher than Parking. Again, a much higher-energy environment electrochemically.

Oh....and yes, you are getting powerfully anal. My metallurgical opinion: Fa'gedabotit!

[Will Durant]

This is much about not much.Hydrogen embritlement is the result of plating (sometimes)not phosphating.I worked some years ago at a company that made landing gear components for the 747 that were phosphated-we did not treat for Hydrogen Embritellment.Thin stock carbon steel-another story when Hard Chrome plated.Will