ZDP-189: Good, but Flawed??

B

barneywray@yahoo.com

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May 18, 2006
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I don't see info related to ZDP-189 corrosion, so here goes... A recent kitchen knife purchase (yes, ZDP-189 core, laminated, manufacturer not named :>)) has a problem with pitting, that is numerous small nicks in the cutting edge, but not elsewhere. I feared mistreatment, but this seems unlikely. The manufacturer has indicated there may be a problem with the WATER in some parts of the US. This rocked me back. I have a number of damascus and collectable zdp-core folders, so this is scary. Any info regarding any such known problems or possible solutions, much appreciated.
- Barney, Knoxville TN
 
I have seen the same thing when soaking a Calypso Jr. in ZDP-189, however it is very unlikely to have it happen at the very edge. It is just random chance where rust forms. Based on the soaks I have done it seems similar to S30V. Yes it can rust readily if left in salt/acidic solutions and if this happens to be on the very edge it will tear it apart. You might want to ask Spyderco if they have q-fog numbers.

-Cliff
 
Barney, are you on well water as opposed to city/municipal water? I treat/fix water for a living and am interested whether it's low PH or Chlorine.
 
Hi - We are are city water, which is somewhat hard, and is chlorinated. A pool test strip shows Chlorine 1 (ppm?), Bromine 3, pH 7.0, total alkalinity 80.

Regarding the "soak", I have taken unusual steps to keep this knife in good condition - so no prolonged wetness or soiling. In fact, none of our kitchen knives rust very often, or show this type of damage at the edge, which is why I'm so curious about this. I would expect the ZDP knife to be the Last in our house to have any problem... but that is Not the case... Well, I have gone back and examined the edge under 8x, and indeed there is some fine rusting. Still, the pitting is really, almost entirely (99%) limited to the ground edge, which is maybe 10% of the core width across the face of the blade.

Am I missing something, like ZDP is more susceptible to rust than more common fine blade steels, to the point of requiring unusual protection?

Thanks, Barney
 
Not that I have seen compared to other high alloy stainless steels, none of them do well if soaked in salt water or acidic solutions, but they don't tend to corrode while cutting. Edges can often attract more rust if they are left with a rough finish, you could also be seeing deposits left from carbon steel blades if you sharpen them on the same stones, that is usually a rare happening though.

-Cliff
 
Cliff Stamp said:
Not that I have seen compared to other high alloy stainless steels, none of them do well if soaked in salt water or acidic solutions, but they don't tend to corrode while cutting.
Click to expand...

Just as a side note of interest even 18/8 stainless steel - as in table flatware cutlery - will show rust and pitting if soaked in water with bleach....

--
Vincent
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Curious if anyone has any other information to add here. Perhaps this has something to do with a galvanic reaction? Not sure if that applies here as i dont know what the laminated steel was and thus if they are much different. Electron migraton causing increased corrosion?
 
Hi Barney, Cliff,

We've not had complaints, but we've only had product in the "real world" for a short while.

We don't have Q-fog numbers on ZDP. It's probably a good time to do another test though. There are a few new steels we'd like to test.

sal
 
Some municipal water systems are better then others. Depending on where you live, you could have really good water or water that barely meets EPA standards. These differences could affect your knives.

I have had ATS-34 rust on me. Not to the point of pitting but, serious oxidation of the factory polished flats. The blade was brittle so, I attributed part of this to a bad heat treat.

I have read limited reports of some kitchen knives that have shown similar effects from kitchen use by careful users on other forums. All of them were related to some secret stainless steel coming from Japan.
 
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