darkening plain carbon steel

ATX

ATX

Joined
Jun 5, 2008
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I am trying to determine the best way to put a darkened finish on a plain carbon blade for a tactical knife. Can someone please tell me the preferred method of darkening a carbon blade, the reason the method is preferred, and how tough the finish will be. Thanks for the help in advance.
 
I am sure there are other methods but gun barrel bluing would work (usually available at Walmart or gun stores). If you want a no shine satin finish (dull grey), I have had good success using an aggregate tumbler. For aggregate I use white aquarium gravel mixed with mineral oil and I tumble the blade in this mixture for about 8 hours.
 
I used ferric acid (radio shack) on some utility knifes and the finish was a medium gray and has held up really well. I think alot of tatical knives have a coating this is a oxidation layer.
 
Dennis
I have not used this on a tactical,but I use ferric to darken carbon blades.Soak for abut a min. then pull out and steel wool and soak again. I do about 4 soaks to get a ood deep gray nd it holds up fairly well.
Stan
 
I have a new son in law who is in the Marine Corp. Thought I would make him a good knife to take when he gets deployed. Just trying to determine the best way to get a dark non glare finish. Unfortunately, my work has been primarily carbon steel and not stainless, so I made a deal with him. I would make him a knife and he would learn to take care of it. He's a good kid and I want to get this right for him.
 
I find that a good ferric chloride etch works very well on carbon steel and holds up very well (just don't go crazy with how deep you do the etch). A nice thing about having the etch is that you can put something like militec-1 on it and it will will stay for a long time, protecting it - due to the microscopic roughness of the etch. On a polished blade it will be gone in a short time. Similar effect with most other protective oils and waxes. Don't use any sort of blueing -- one, it doesn't last long and quickly begins to look terrible with use; two, blueing is not intended for use on anything that you might use to cut and prepare food - it will release nasty tasting and toxic chemicals when you do, especially with anything acidic.
 
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I am getting ready to Parkerize a knife I made for my stepson, who is also in the Marines. I would offer to do yours but this will be my first attempt so I am not confident enough to do so yet.
Parkerizing is the black finish that is typically found on military firearms and is supposed to be tougher than blueing and offer better rust resistance. Many gunsmiths can do this for you. It is not difficult to do yourself but will cost 75$-150$ initial outlay to get set up, depending on what items you already have. It may not be worth setting up to do just one knife though.
 
I have gotten a real dark finish soaking the blade in a liquid bleach/vinegar mix for about 15 minutes. Almost looks blued.
 
Can anyone that Parkerized a blade comment on how it turned out? Any disadvantaged to Parkerized finish?
 
Thanks everyone. I think I am going to try the Parkerized finish and see how it turns out. Anyone have any photos of blades that have been parkerized, I would appreciate a peek at them.

Will the Parkerization method damage the edge retention on the blade?
 
It should not affect the edge other than the black coloring.

The process is pretty simple. It requires the surface to be somewhat rough, it supposedly will not work well on a polished surface. An acid-washed or abrasive-blasted base finish is supposed to work well.
Other than that you need to completely clean and degrease the blade, and immerse it in the Parkerizing solution for 15-45 minutes. The solution has to be held at about 190 degrees F. and needs to be in a stainless container.
I am hoping to do 2 blades this weekend so I will hopefully have some results to share.
 
Parkerizing works best on a freshly sand or bead blasted part. Sand blasting is preferred over bead blasting but I have had success using both blasting techniques. I have also just used fine sandpaper to prepare steel also with good results. I usually Manganese parkerize (BLack) but have also done the grey color parkerizing called zinc parkerizing. I have a article on my website on how I park guns if you care to read it.
Chris
 
I, once use a product from home depot
call "phosphoric prep & etch"
after a beatblasted.

and finish whit a coat of militec-1
 
I've done cold "black oxide" finish, ferric etching, and parkerizing... but so far my favorite has been paying someone else to do a professional black oxide finish.

The parkerized finish can look chalky and un-even (the tint changes based on steel hardness levels). Pics on my site show parkerized spikes and knives.

Note that there are two kinds of parkerizing solution; one leaves a grey finish; the other, black (like Blindhog said).

The black oxide finish is more durable, sleeker (bead-blast prep as opposed to a sandblast prep), and much more consistent in appearance. AKA hot bluing.
 
I just put this finish on some old Dexter knives that I re-made. I just poured muriatic acid from the hardware store on the blade and let it sit for an hour or so. Might not be what you are looking for though...

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