Forced patina on CPM D2

M

Mark Redmon

Well-Known Member
I was curious if anyone else has had an issue getting CPM D2 to take on a patina. When I first started making knives a few years ago, I made a few out of Admiral's D2. I decided to play around with a mustard and vinegar finish and found that it would take on a nice dark mottled look with a few applications. Soon after, I started using stainless for most of my projects, so forcing a patina was a non-issue. After living with and evaluating a few of those early D2 knives for a few years, I decided it really needed to be back in the mix. Recently, I purchased some CPM D2 from Niagara. I've made several knives from this so far, and it's really nice stuff.

So here is the issue: I am making a knife for a friend of mine, and he was definitely leaning toward a darkened blade. I'm not really into sprayed coatings, so we talked about a vinegar patina. I thought it would be a piece of cake (based on past experience), but I can't get it to take on much color. I realize all steels aren't created equal, but should it be that much better in corrosion resistance? What I've tried at the point is yellow mustard, warm vinegar and formula 44-40 separately.

I apologize for the long winded explanation... just thought I should give some background.... or maybe I'm just a long winded kinda guy. At any rate, I'd like to hear any opinions. Should I just go with a rubbed finish, or is there something I can do (short of changing the steel) to get this thing dark?
 
It's a good question; I'm guessing the finer grain of the CPM is protecting it better? The Caswell stuff looks promising if you want an even grey/black color. (scroll down the page for Blackener 370 for stainless).
 
Thanks James, I've looked at that stuff in the past, but forgot about it until you mentioned it. If I go that route, I'll let you know the results.
 
Thanks Brian... I might give that a shot. I'll try to get out to one of the Radio Shacks and see if I can find some this weekend... although they are all more like cel phone shops these days.
 
Mark Redmon said:
Thanks Brian... I might give that a shot. I'll try to get out to one of the Radio Shacks and see if I can find some this weekend... although they are all more like cel phone shops these days.
Click to expand...

Your right I remember Rat shack when the whole place was build it youself crystal radios and various other kits for a young feller to try to electocute him self with.The youth today can have no fun.
Stan
 
You're right about that Stan!
Cliff - it's night and day compared to the non-CPM D2 I was working with a few years ago. I was shocked at the fact that the 44/40 didn't touch it at all. Overnight in white vinegar just gave it a few hazy spots. It's not the end of the world if this doesn't work. Like I said, this one is for a friend, and I'm sure he'll understand. I just couldn't believe how difficult the CPM D2 was to get a patina on. I guess that's a good thing....
 
I've been wanting to make some period looking knives with a patina but never thought of trying D2. Didn't figure it would take it well. Did you dip it in mustard and vinegar or just rub it on?
 
Cliff- I wasn't sure it was going to work either, but I gave it a try. I basically dabbed on some yellow mustard and let it dry, then used a spray bottle with white vinegar to saturate the blade. I let it sit for about an hour...maybe 90 minutes, then rinsed the mustard goop off, and gave it a good rub with 0000 steel wool, then repeated the process maybe 3-5 more times. Sorry about the bad pic, but it's an older knife, and all I can find at the moment...

lfsan.jpg
 
I've used a 10% solution ferric chloride and distilled water. Works great. Takes about 10 minutes.
-John
 
Cliff- It's been a while, but I probably had it to at least 6-800. It may have been higher, but I don't think there would be much benefit to that.
 
Hey guys,
I've got my FeCl3, but it's wayyyyy too cold to be out in the shop right now. There is one thing I was wondering... do you lay the blade flat in a pan, or would it be better to suspend it vertically in a length of PVC pipe or something? The finish really must be as even as possible, and I know that can be achieved (at least based on the work I've seen by others), I just wasn't sure what the proper set up would be.
 
Tall and thin,suspend it in a container,I use a rubbermaid container holds about a quart and is 10"tall.
Stan
 
Thanks Stan.... That's kind of what I was thinking. Do you think temperature would matter? I doesn't look like we'll have many days with highs above freezing anytime soon.
 
I don't know about FeCl but vinegar works a lot faster when it's hot (don't do it in the house, the whole place will reek). In general more heat speeds up any chemical reaction. Check it out before you go heating/boiling ANY acid or base though, the fumes might be very dangerous!
 
Thanks for the reply James. Luckily, my fiance is in to knives, and doesn't mind "the process". I've vinegar'd up the house a few times... she said it smelled like Easter. I didn't really plan on boiling the FeCl, but was thinking room temp versus 30 degrees... I guess I'll dilute it in the house (maybe with warm water), then take it out to the shop for the dip.
 
Cheap candle warmers, or coffee cup warmers are great for this type thing.
When I used to break taps on a regular basis, I'd put my acid jar on a coffee cup heater outside.
Sped up the process dramatically.

There's also a tiny Crock-Pot made that we just got for $10
I use it like a double boiler
 
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