ZDP-189 Patina

[MadMaximus]

Has anyone forced a patina on a ZDP-189 knife? I think it would look good with the green handle of my Endura. Just wondering! Pics appreciated! :D :spyder: Thanks!

[Cliff Stamp]

Lots of people have forced it on steels which are more stainless, you just have to use a strong etchant. If you are going to do it then protect the edge and as with any corrosion agent know what you are doing and how to dispose of it.

[MadMaximus]

Yeah I've done that, but I was wondering if anyone did anything with ZDP specifically. Just wondering what they've used. Was also wondering if cider vinegar would work like it does with carbon steel.

[PayneTrain]

My Stretch seems to be forming one naturally, so it can't be too hard. It's very faint and sometimes it doesn't even seem to be there, but it actually looks really cool sort of like a pearl coat on a car. I use the knife mostly for food so I imagine any of the traditional acids people use from their kitchens will work on ZDP to force the patina. Might just be a little slower.

[JD Spydo]

I can give you one thing to be aware of concerning ZDP-189 blade steel. First of all it's one of my top 5 favorites so this by no way is considered a slam against the blade steel but rather a "heads up" warning. I can tell you first hand ZDP-189 does not resist food acids very good at all. A few years back one summer night I was cutting up some tomatoes with my Burgundy Caly Jr. that had ZDP-189 blade steel.

I did a really dumb thing and forgot to wash it off with fresh water and dish soap. The next day it was as though termites had been eating at it. There were literally noticable notches and dings on the blade's edge. It was so bad on the edge that I had to actually send it back to the factory and they re-ground the edge back to normal. If it wasn't for the 420 stainless outer layer I hate to think what all would have happened to it. So please by all means don't play with any patina experiments and do keep your ZDP-189 blades well washed and it wouldn't even hurt to keep an oil coating on it. That's what I do to my ZDP-189 blades since then.

Now I realize that the home grown tomatoes had a high acid content. But I had never ever had that happen to any of my stainless blades prior to that incident. So beware of food acids or anything that could potentially corode the blade.

[Cliff Stamp]

Yeah I've done that, but I was wondering if anyone did anything with ZDP specifically.

Yes, you can read about it on BladeForums, ferric chloride or similar is recommended - note this is not similar to vinegar in regards to handling/breathing/disposing.

I can tell you first hand ZDP-189 does not resist food acids very good at all.

ZDP-189 like many stainless steels has a temper cycle which is high, if this is used then the corrosion resistance is severely compromised. I don't know which cycle Spyderco uses, but if you want high corrosion resistance you need to :

-soak hot
-quench very fast
-temper low

This is true of any stainless.

[JD Spydo]

ZDP-189 like many stainless steels has a temper cycle which is high, if this is used then the corrosion resistance is severely compromised. I don't know which cycle Spyderco uses, but if you want high corrosion resistance you need to :

Well Cliff I can tell you when I had this happen to me after cutting up the tomatoes I truly was shocked at the stunning damage it did to the ZDP-189 blade on the Caly Jr. The only reason I was using it at the time because it was one of my EDCs and it was handy. I had no idea that the ZDP-189 didn't have any better corrosion resistance than that. I had previously used the Caly Jr. and 2 other ZDP-189 blades on hot days when I was even sweating profusely and even that didn't seem to cause the problem that the acid from the tomatoes did. It was a lesson I won't forget and I'm wondering what other food acids would do similar damage. But I'm not going to find out because I'm going to keep all my blades clean after usage regardless of how corrosion resistant they claim to be.

Since then I've been using Sentry Solutions "TUF CLOTH" to rub down my ZDP-189 blades as well as most of the VG-10 blades that I use often. Haven't had a problem since. What's really freaky about the incident is that I really doubt if it would have done any worse damage on a carbon steel blade. The amount of damage that it did overnight was just mind boggling. I always appreciate your feedback. Interesting thread.

[O,just,O]

And you ate that tomatoe :eek: .
O.

[D-Roc]

I seem to have a faint bit on my E4 FFG grey...its faint, and its not all over the blade, just in about half the area. Not sure how it got there, wasn't intentional. Possibly I accidentally left it in the dishwasher or was using it in the kitchen.
This particular blade seems to pic up faint rust spots as well. Strange because my E4 CE is the exact same steel. Not a big deal because I find the rust spots simply wipe off with a bit of non toxic mineral oil.

[Cliff Stamp]

Well Cliff I can tell you when I had this happen to me after cutting up the tomatoes ...

To clarify, I am not saying that you didn't experience low corrosion resistance on ZDP-189, I am just saying that this steel has a high temper cycle and if that is used then the corrosion resistance will be severely reduced. Thus it isn't clear that you are seeing the behavior inherent in ZDP-189, it could just be how it was hardened.

[Jazz]

I love the light patina or darkness that ZDP takes on. Just ever so light - looks great.

[bearfacedkiller]

Hmmm... Seems very corrosion resistant to me. I do live in a dry climate though.

[Donut]

To clarify, I am not saying that you didn't experience low corrosion resistance on ZDP-189, I am just saying that this steel has a high temper cycle and if that is used then the corrosion resistance will be severely reduced. Thus it isn't clear that you are seeing the behavior inherent in ZDP-189, it could just be how it was hardened.

Hey Cliff, thanks for mentioning this.

I have a knife in CPM-S30V that shows some staining. Like, slight discoloration over a period of a few months. I bought it on the secondary market and it had spots and stuff all over the blade, Flitz was the only thing that removed them and it brought it to like new. I thought it was a fluke, but a few months passed and there is a cloudiness to the blade.

From your statement, it sounds like it could be the heat treat. Would that be a good or a bad thing?

[Cliff Stamp]

Would that be a good or a bad thing?

As a bit of history, there was a time when most stainless steel was air quenched and tempered hot, to question this was extreme as Paul Bos did it that way and a number of custom knifemakers who used Bos were extremely vocal that it had to be done that way.

A number of people noted that the metallurgy certainly did not say that, but it took Ernest Mayer of BlackCloud knives to be the first knifemaker to in public argue that Bos (and everyone else who made that argument) was wrong, high tempers reduced performance.

The outcry was high, but eventually it became clear, no matter what source you checked it all said the same thing, and eventually even Bos had to change because high tempers reduce toughness and corrosion resistance and compromise the apex stability.

Why was it done - because it is cheaper/easier to run high tempers.

--

If you have a stainless steel knife which has lower corrosion resistance then there are a few things you should check :

-do you sharpen it with stones which work on non-stainless steel
-do you use it to cut/around very corrosive chemicals
-is the surface really scratched up

These things can all cause problems even if the hardening is optimal, but if none of them are relevant it could be :

-the knife was not soaked hot enough
-it was cooled too slow (air vs oil)
-it was tempered hot

If this is the case you can reharden it, but it isn't simple and the guy doing it has to know what they are doing and in most cases you would actually be better of selling it and getting another knife made for the cost of a one-shot rehardening.

[Donut]

I sharpen it with stones that I sharpen non stainless with, too. I think that's what you're asking.

I don't cut anything very corrosive. Some food, then I clean it.

The surface isn't scratched.


I'll try to verify the performance with a little testing.

[EnduraNCE]

So I’ve treated my Endura 4 like three times with tuf-glide. Then, a day in my pocket and some fidgeting it gets little brown dots where my thumb oils touch. It’s really bugging me cause I got this as an EDC.. did some lacking research and was under the impression the stuff is a more corrosion resistant VG10.

Anyways, what can I do to keep the ZDP189 looking nice but having me be able to touch it. Wiping the oils off did nothing to help.

[Michael Janich]

Dear EnduraNCE:

Welcome to the Spyderco Forum.

Although ZDP-189 has a very high chromium content, that is offset by an extremely high carbon content, which means it is still likely to patina.

Stay safe,

Mike

[JSumm]

So I’ve treated my Endura 4 like three times with tuf-glide. Then, a day in my pocket and some fidgeting it gets little brown dots where my thumb oils touch. It’s really bugging me cause I got this as an EDC.. did some lacking research and was under the impression the stuff is a more corrosion resistant VG10.

Anyways, what can I do to keep the ZDP189 looking nice but having me be able to touch it. Wiping the oils off did nothing to help.

I only have one knife with ZDP-189. Have not had it long at all, but it seems to develop rust spots easier than anything else I have. Even K390. I don't know if it is left over shaving dust from sharpening. It is always along the edge. It wipes right off too. I have not seen any patina yet. So it appears that ZDP-189 is fairly stainless, but not very corrosion resistant. Maybe those two things can be related but different.

If it doesn't wipe off then maybe some Flitz to remove. In the past, I have just used Vaseline to coat.

[metaphoricalsimile]

did some lacking research and was under the impression the stuff is a more corrosion resistant VG10.

ZDP is *less* corrosion resistant than VG-10 with *more* edge holding.

[Makunochimaster]

imho, corrosion level ZDP-189 approximately at the level D2 or CTS-XHP