Parkerizing and Hydrogen Embrittlement

[mdoerner]

Hi All,

I just re-parked my bolt to get rid of the Greek Black coating/finish. I remember someone on the old forums saying to wait 7 days before using it due to hydrogen embrittlement, others say bake at 200 Deg F for 2 hours to relieve it. Which is right? Thanks in advance.

Mike Doerner

Information

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[mdoerner]

If it makes any difference, my bolt was de-greased with bore blaster, then bead blasted in the cabinet. No naval jelly or other chemical strippers were used.

Mike Doerner

[gunny33]

Hi All,

I just re-parked my bolt to get rid of the Greek Black coating/finish. I remember someone on the old forums saying to wait 7 days before using it due to hydrogen embrittlement, others say bake at 200 Deg F for 2 hours to relieve it. Which is right? Thanks in advance.

Mike Doerner

Hi Mike,
The plating house I work for does phosphating for several large weapons mfgs [military included]. We bake the phosphated parts at 215 deg for 8 hours. Bead blasting is ok but it folds the metal over leaving a smooth surface. Sandblasting leaves ridges and valleys giving the phosphate a place to deposit itself. No big deal either way, you may see the phosphate coating ware away a little faster is all. Hope this helps.

Bill

[Lt1]

Hi All,

I just re-parked my bolt to get rid of the Greek Black coating/finish. I remember someone on the old forums saying to wait 7 days before using it due to hydrogen embrittlement, others say bake at 200 Deg F for 2 hours to relieve it. Which is right? Thanks in advance.

Mike Doerner

+

Really only applies to springs . Parkerizing springs is a No-No in a basement armory .

[ORM1Garand]

Please don't quote me on this but in my plating days 40 years ago we were baking plated parts @ 375 degrees for three hours . This may be old school technology.

[mdoerner]

Hi Mike,
The plating house I work for does phosphating for several large weapons mfgs [military included]. We bake the phosphated parts at 215 deg for 8 hours. Bead blasting is ok but it folds the metal over leaving a smooth surface. Sandblasting leaves ridges and valleys giving the phosphate a place to deposit itself. No big deal either way, you may see the phosphate coating ware away a little faster is all. Hope this helps.

Bill

OK, but if I didn't do that (bake after parkerizing), the lugs on the bolt aren't going to snap off, right? I'm not as concerned about the durability of the finish than the durability of the bolt itself.....

Mike Doerner

[mdoerner]

And maybe I'm just over-blowing this. Looking at Brownell's instructions, there's nothing in there about elevating temperature or baking parts after parkerizing. An unemployed mechanical engineer with too much time on his hands to overthink non-existant problems? Maybe....;-)

Mike Doerner

[JAS]

I have parkerized several bolts without any additional heat treatment, and I have not had any problems in thousands of rounds. I bead blast them, park them, oil them, and shoot them, in that order. Over 2K rounds on one that I am aware of and no problems. I think you are worrying about a non-existant problem. If you feel better, bake them at 200 to 215 degrees. As an old tool & die maker that has heat treated a lot of steels I can't imagine 215 degrees having any effect what so ever. Now 375 degrees is getting up there where you can start changing the metalurgy and could possibly start warping things. I would be careful about that.

You can do more for safety by properly lapping the bolt in to the lugs in the receiver so that both bolt lugs share the load equally. A lot of guys swap a bolt, check the head space and figure they are good to go. The headspace may be check good, but that headspace may be based on one lug resting on a high spot.

[Devil Dog]

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.

[mdoerner]

While I understand the parts were parkerized before, I wasn't sure if they needed to be relieved of any hydrogen before. Good to know others are NOT having a problem.

Mike Doerner