park question

[shortround13]

This may be answered somewhere but couldn't find, I have 2 kits, one is built and unparked, the other has yet to be built. The unbuilt kit I'm going to park just the receiver and barrel to retain the original used finish of the parts. My question is, what would happen if I only sand blasted the receiver and barrel of the built kit and dipped the whole thing in the park solution? Will it not adhere at all to the unprepped metal, or will it just f it up and make the original trunions trunions other parts look blotchy and like crap?

[Gunsmith Dan]

Yes it will stick ... for awhile but you will notice the unblasted areas will eventually start to flake off.

Used 320 grit sand paper in the areas you can not sand blast to at least give a rough enough surface for the Park to adhere better. Sand in one direction only and in a straight line, do not do circle like sanding.

[shortround13]

I should have specified, I'm wondering if I can keep/protect the original finish of the kit parts if they are dipped but not prepped. Or should I just park the receiver and barrel separately if I'm not looking to alter the finish of the trunions etc.

[Gunsmith Dan]

Yes it is higly recommended that you don't put already parkerized parts into a park bath.

Besides the adhesion issues Parkerizing is a Phosphate Plating process so like all plating processes it changes the dimension of the parts. SO yes you could have parts that no longer fit or are really tight if you parkerize over existing park finish as well.

[bigbob76]

I can't even count how many times I have sandblasted only the built receiver of a reborn AK. I pressed in the original front end that is already Parkerized and put the degreased barreled receiver in the solution. So far every time the results have been perfect.

[kcstott]

I have to agree with Bob on this one.

I've dumped pre parked parts in the bath and had no issues.
They are already parked and will park a little more but very little compared to a raw steel part. I have not notice any dimensional changes that mattered or created fit issues either.

Granted it's not the proper way to do it but this is home builds and as long as it looks good and works it don't matter.

[Gunsmith Dan]

But like I said preping a surface has very little to do with looks and alot to do with adhesion.

Yes already parked parts can parkerized and look somewhat decent, but you will notice the coating flaking off over time. The biggest problem with Park finishes it that they are so porous that oils get trapped to the point even solvent soaking will not remove all of the oils.

It all depends on the amount of work you want to put into redoing something every x number of months/years. If done correctly from the beginning you can get a finish that will never come off even many years from now .... look at alot of old military rifles that still have the original parkerized finish from 50+ years ago and the finish will only come off after blasting or sanding them off.

[kcstott]

But like I said preping a surface has very little to do with looks and alot to do with adhesion.

Yes already parked parts can parkerized and look somewhat decent, but you will notice the coating flaking off over time. The biggest problem with Park finishes it that they are so porous that oils get trapped to the point even solvent soaking will not remove all of the oils.

It all depends on the amount of work you want to put into redoing something every x number of months/years. If done correctly from the beginning you can get a finish that will never come off even many years from now .... look at alot of old military rifles that still have the original parkerized finish from 50+ years ago and the finish will only come off after blasting or sanding them off.

Yes but if I took a preparked M1 Garand receiver that had an in the white barrel on it, if I degreased the receiver and blasted the barrel then parked it. the little bit of additional parkerizing that will occur on the receiver will not cause the original underlying parkerizing to some how go sour. It will still be there in all it's glory and be just fine.
Yes you run the risk of mildly discoloring your original parts. Yes you run the risk of contaminating your park solution. But your parts will be fine.

Remember the OP is asking about dipping an assembly of original finished parts attached to a receiver in the white..

Mask off your barrel, front trunnion, and rear sight block. Blast the receiver, clean everything and dunk it in the park tank, it will be fine.

[bigbob76]

Yes it will stick ... for awhile but you will notice the unblasted areas will eventually start to flake off.

Used 320 grit sand paper in the areas you can not sand blast to at least give a rough enough surface for the Park to adhere better. Sand in one direction only and in a straight line, do not do circle like sanding.

Yes it is higly recommended that you don't put already parkerized parts into a park bath.

Besides the adhesion issues Parkerizing is a Phosphate Plating process so like all plating processes it changes the dimension of the parts. SO yes you could have parts that no longer fit or are really tight if you parkerize over existing park finish as well.

I guess I've always thought of Parkerizing as a treatment to the surface of steel. I have so far never read anything about it being considered a "plating" and I have definitely never seen it "flake off". But then again I only have a few years experience with Parkerizing.

[ar15barrels]

I guess I've always thought of Parkerizing as a treatment to the surface of steel. I have so far never read anything about it being considered a "plating" and I have definitely never seen it "flake off". But then again I only have a few years experience with Parkerizing.

Parkerizing is a "surface conversion" treatment.
It is NOT a plating.
It does not ADD anything.
It converts the existing surface of the metal.
There is NOTHING that can "flake off" unless it is paint or crusty oil/grease/dirt, all of which should be removed before the parts go into the park bath.

[Gunsmith Dan]

No....

Parkerizing is a Phosphate Conversion coating, not a Surface Conversion Coating.

Hot Caustic Bluing / Hi Temp Black Oxide.... A Surface Conversion Coating ..... takes a chemical process and forces elements into the parent material to form a different compound related to the parent material. In this case it forces additional oxygen into the iron on the surface to form a a Black Oxide (black rust) called Magnetite (rust removers remove oxygen from iron which is why they remove bluing).

There is almost no dimensional change ( measured in the 10 Thousands of a inch) just the slight increase to make room for the added oxygen.


Parkerizing / Phosphate Conversion Coating / Electroless Plating .... A Chemical Conversion Coating ..... is a electrochemical process that takes materials added to a chemical solution through a chemical reaction extract certain elements out of the solution and deposit them onto the surface of the material to be coated in crystaline form that because of the chemical reaction fuses/plates them to the surface. BTW Electroless Nickel is a Nickel Phosphate coating, you could say it is a Nickel Parkerized type of finish.

Chemical Conversion Coatings do change dimensional tolerances, depending on material, bath type and time can be as thick as 3 thousands of an inch, even more in some cases. While most parkerized finishes are done as a thin coating they can add as much as 0.5 Thousands of and inch (1/2 mill) to the surface which makes it look like they do not change tolerances on Military style firearms that have loose tolerances.