Gunsmithing Cerakote over nitride?

[Lrdchaos]

I’m looking at building a rifle and really like the impact 737/787 action. I want the Metal to be fde, can I cerakote the exterior portion of the action and leave the interior nitride?

 

[308pirate]

Yes. It's just paint. Mask whatever you don't want colored.

Not sure what the fact that the steel's nitrided (which is a heat treatment, not a cosmetic coating) has to do with this anyway.

 

[hino895]

Yes but you will need to blast the exterior first.
What I did was make a plug out of a wooden dowel.
Hit the hardware store and buy one that is the closest diameter.
Too big whittle it down
Too small wrap it with tape, make it fit tight.

 

[Ledzep]

The black surface from nitride is a byproduct. The hardness & physical properties it gives go a shallow depth into the surface. Blasting the black away won't remove the nitride treatment, just the black color.

 

[GH41]

Led, Would you agree that a nitride finish is hard enough that no additional grip for the paint would be gained by media blasting it?

 

[gnochi]

Led, Would you agree that a nitride finish is hard enough that no additional grip for the paint would be gained by media blasting it?

I’ve sandblasted nitride before and the top layer comes off easily enough, and gives you a good adhesion surface.

You can’t get adhesion to that top layer; peel strength of every adhesive material I tried was literally zero.

 

[Ledzep]

Led, Would you agree that a nitride finish is hard enough that no additional grip for the paint would be gained by media blasting it?

No. Sand/glass is harder than steel (thought not near as tough). It will still move the surface material around and change surface roughness.

 

[longshot2000]

have you ever tried to remove enough of the exterior nitride in CMV steel to then phosphate the exterior? I have never heard anyone answer this before. The nitride treatment in the bore is great, but if one wanted a traditional phosphate / Parkerized finish, can aluminum oxide media blast away enough of the nitride surface ?

 

[gnochi]

have you ever tried to remove enough of the exterior nitride in CMV steel to then phosphate the exterior? I have never heard anyone answer this before. The nitride treatment in the bore is great, but if one wanted a traditional phosphate / Parkerized finish, can aluminum oxide media blast away enough of the nitride surface ?

I’m not sure why anyone would ever do that, because Nitriding is better in literally every measurable way. If you want a more diffuse surface, you just start with grit-blasted material and skip the “polish” stage of quench-polish-quench.

The ”white” layer (which gives the anti-corrosion properties) is easy to remove with blasting media and is up to ~5 tenths thick, but the diffuse layer that gives the mechanical properties is typically 4-8 thou thick and that’s a lot of material to remove just to give a different finish. I can’t speak to how nicely phosphating and nitride diffusion play together but I wouldn’t expect good results.

 

[Mike_P]

The hardness isn’t necessarily the key to adhesion. You can also lightly buff the outside by hand with a piece of scotch bright as your prep.
You’re creating the smallest of ridges for the cerakote to adhere to.

As far as leaving the inside of the action nitrided it’s VERY easy. I do it all the time with nitrided parts and even microslicked. 2 high heat plugs and a couple pieces of tape and you’re good to go.

As previously stated the black is a byproduct or dye that has no bearing on the treatment. So don’t worry about losing it externally. Cerakote is typically within 1-3 mils of thickness so very little is needed and shouldn’t affect any tolerances when applied appropriately.