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Japanese knives ZDP189


CommissionerLin

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I agree that no stainless (except H1) is completely rustproof, but based on my personal experience and that of other knife nuts I think you'll find that ZDP189 is far more prone to both surface rust and pitting than any of the normal stainless steels used in high end kitchen cutlery (e.g. 440 a and c, VG10, and S30V). 

... Try the lemon juice test and see...

I did (on the JCK Sanetu ZDP189 Santoku).

10 minutes.

No marking whatsoever on the side of the knife. (Where I put the juice drops.)

Whatever the effect might be on the exposed cutting blade of the magic stuff, the stainless cladding is just as mirror-pretty as before...

Phew! :smile:

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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I'm sorry if I wasn't clear in my posts. It's ZDP189 that is prone to corrosion, not the ATS-34 on the sides. The sides of these knives should be worry free. It's the core of the knife that is of concern (i.e. the part that does the actual cutting).

It seems that practically all the makers of ZDP189 blades are aware of the rust issue. These knives are all being offered now either clad in a more stainless steel or with a durable coating on the blade. Such knives will stay nice and pretty even if the edge rusts away...

Try the lemon test on the ZDP189 part, if you dare. :unsure:

Any dish you make will only taste as good as the ingredients you put into it. If you use poor quality meats, old herbs and tasteless winter tomatoes I don’t even want to hear that the lasagna recipe I gave you turned out poorly. You're a cook, not a magician.

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...

Try the lemon test on the ZDP189 part, if you dare. :unsure:

In my case, no way until after I have adequate sharpening technology in place to re-dress things. :hmmm:

And a microscope, and a few control knives for comparison...

I wouldn't ordinarily leave anything acid on any knife for any length of time.

I would expect *any* clad knife to tend to have more corrosion problems than a knife of uniform composition.

Where you have two dissimilar metals, in electrical contact and both in contact with an electrolyte, you have an electrochemical corrosion cell. The cell voltage (influencing corrosion rate) depends on the difference between the two metals "electrochemical potential". And IIRC even different heat treatments (and different mechanical working) can give rise to different potentials.

From what I know of why lightening conductors work (increased charge density at the sharp point), I'd expect any corrosion of any clad knife to be most evident on the sharpened edge, because it is an electro chemical process, and that's where the field would be strongest, ion transport easiest, etc.

I don't believe I have any other clad knives to compare it with, to see whether the effect is distinctly worse with ZDP189.

However, I do recall the lore that Tomato blunts knives disproportionately quickly. My suspicion has been that that this was due to the acidity of the tomato, rather than any great toughness of the skin. And the lore dates from the time when all good knives were "steel" (not stainless).

I'm enjoying using this knife. It goes through onion and carrot... well... "like a knife through butter". Now, while I know this is largely a sharpening thing, my hope and expectation is that this knife will hold this extreme edge way better than something more traditional.

And for that, I'm prepared to nanny it a bit.

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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As a scientist and owner of one boat (and responsible for four work boats) used and sometimes left in saltwater I am painfully aware of galvanic corrosion. However, in knives this is not a problem. In fact, the cladding is typically used to prevent corrosion and discoloring (and/or to add toughness).

I'm sounding like a broken record, so I'll stop. I wish you luck. So long as you do some light oiling after using the knife, you will probably end up loving the incredible wear resistance of ZDP189.

Any dish you make will only taste as good as the ingredients you put into it. If you use poor quality meats, old herbs and tasteless winter tomatoes I don’t even want to hear that the lasagna recipe I gave you turned out poorly. You're a cook, not a magician.

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Thanks Mike and thanks for the warning!

To just nail this (hopefully finally)

... I am painfully aware of galvanic corrosion.  However, in knives this is not a problem.  In fact, the cladding is typically used to prevent corrosion and discoloring (and/or to add toughness). 

Yes, aware of the toughness and cosmetic (perhaps frictional) reasons for the cladding.

My point was that corrosion will be focussed at the sharp edge of the blade, and the sharper the blade, the more the edge would be subject to attack.

Secondly, for a corrosion cell, you ideally need two dissimilar metals - and in that respect the cladding could actually exacerbate the problem.

This thing has a pretty acute edge (anyone measured the angle yet?) - so with the cladding layer to provide the second electrode there exists considerable 'potential' ( :rolleyes: ) for corrosive dulling of the edge.

It may even be that this, rather than wear, will determine the need for resharpening.

In the meantime, I'll treat it kindly!

As a final point, the strange "no pumpkin or pineapple" leaflet appears to be general guidance from JCK rather than being specific to ZDP189.

"If you wish to make an apple pie from scratch ... you must first invent the universe." - Carl Sagan

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I'd like to hear from a metalurgist on this, but my impression is that clad metals don't present any galvanic corosion issue. You need more than just two "dissimilar" metals. They need to be dissimilar in a way that one behaves like an anion or cation relative to the other, and you need some kind of electrolite between them.

When you have this kind of condition, the whole assembly turns into a battery, and the metals deteriorate pretty quickly. I remember this being an issue with some early generation carbon fiber bicycles, that were made by gluing carbon fiber tubes into aluminum lugs. There's a relative charge between the carbon and the aluminum, and the epoxy being used functioned perfectly as an electrolyte. The bikes performed beautifully, and then in a few weeks spontaneously fell apart.

Kasumi style knives, with various kinds of stainless and carbon steels clad in various kinds of iron and other stainless steels, have been around for a long time. And if there were issues with galvanic corrosion, you'd expect to see it between the clad layers, resulting in the knives delaminating. I wouldn't expect it to express itself as rust on the cutting edge.

Notes from the underbelly

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Do you people honeslty think that a carbon steel knives wears down so fast that you have to be so protective of it? Oil it every day? Edge rusting away? Do you think those 40-50 year old carbon knives never touched acid in foods? I only have two SS knives in the bunch and all my carbon knives have NEVER formed any rust and no oil was ever applied. Applying oil does not extend the life of your knife. Unless you sharpen it down to nothing your knife will be here long after you're gone.

These knives are not left in salt water 24/7 and dissimilar blade materials is not the cause of having to sharpen once a month due to corrosion. Good grief. You have to sharpen because you bang your edge against the cutting board, not because your knife was exposed to the volitile combination of food, water and oxygen.

The cladding is put there to support the hardness of the core. Nothing mysterious. The cladding can either be "stainless" or wrought iron depending on what the maker wants to use and the type of knife. The purpose for using a stainless is so the people that freak out because a patina might form on their knife can rest at ease and keep their knife looking pretty. Oh yeah, and it's softer than the core it's surrounding.

My Photography: Bob Worthington Photography

 

My music: Coronado Big Band
 

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The cladding is put there to support the hardness of the core.  Nothing mysterious.  The cladding can either be "stainless" or wrought iron depending on what the maker wants to use and the type of knife.  The purpose for using a stainless is so the people that freak out because a patina might form on their knife can rest at ease and keep their knife looking pretty.  Oh yeah, and it's softer than the core it's surrounding.

It's just not true, in this case, that a softer material is needed to "support the core." I think your second statement is right- it's just to keep the knife pretty.

I agree that the rust is not a huge issue, or that it will appreciably shorten blade life. It's just ugly, and something to keep in mind in terms of not letting the blade sit in the sink or on a damp dishcloth overnight.

Any dish you make will only taste as good as the ingredients you put into it. If you use poor quality meats, old herbs and tasteless winter tomatoes I don’t even want to hear that the lasagna recipe I gave you turned out poorly. You're a cook, not a magician.

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The cladding is put there to support the hardness of the core.  Nothing mysterious.  The cladding can either be "stainless" or wrought iron depending on what the maker wants to use and the type of knife.  The purpose for using a stainless is so the people that freak out because a patina might form on their knife can rest at ease and keep their knife looking pretty.  Oh yeah, and it's softer than the core it's surrounding.

It's just not true, in this case, that a softer material is needed to "support the core." I think your second statement is right- it's just to keep the knife pretty.

I agree that the rust is not a huge issue, or that it will appreciably shorten blade life. It's just ugly, and something to keep in mind in terms of not letting the blade sit in the sink or on a damp dishcloth overnight.

Really? Why are Ryusen Blazen knives San Mai made? Why are Artisan knives San Mai made? Why do you think Ikeda knives are San Mai made? I could go on with a whole slew of knives that have a stainless core that are also stainless clad. Unless the knife is a Honyaki, it would be difficult to find any blade with a high HRC rating that the ZDP189 has that is not surrounded by a softer material for support. Look at all those knives made with tool steels (SRS-15 and the like)...they are ALL clad and they are ALL stainless. Why do you think that is? Even carbon core knives are clad in carbon so what do you think the point of that is if the carbon cladding never becomes part of the edge? It's certainly not there to make the knife look pretty. It's not there because the manufacturers are trying to be inventive. The whole purpose behind this warikomi method of construction is to give strength to a very hard and brittle metal core and this method has been around for a hundreds and hundreds and even more hundreds of years. The only differences between then and now are the materials used.

My Photography: Bob Worthington Photography

 

My music: Coronado Big Band
 

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I recieved my ZDP-189 along with a Gekko nakiri from JCK yesterday. It took no more than 5 days to get here. No added tax or duty was charged at the post office.

Out of the box, the ZDP-169 and the Gekko nakiri looked like a pieces of jewelry, just beautiful. The Cocobolo wood on the ZDP and the mahogany on the nakiri handle only adds to the beauty of the knives, no burrs, no sharp edges, good for small hands, balance is good as far as Japanese knives go. I put both to work preparing for Sunday brunch with my nephews and my brother. No visible signs of rust or stainning. The Nakiri is sharpest knife I've ever used but the ZDP-189 needs a little time on a stone, this is in contrast to the beautiful Gekko Nakiri's scary sharpness out of the box. Both knives are a work of art and would recommend it them to anyone. I may get another ZDP-189 but it seems that it is sold out again, along with a Hattori wa-gyuto.

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The cladding is put there to support the hardness of the core. Nothing mysterious. The cladding can either be "stainless" or wrought iron depending on what the maker wants to use and the type of knife. The purpose for using a stainless is so the people that freak out because a patina might form on their knife can rest at ease and keep their knife looking pretty. Oh yeah, and it's softer than the core it's surrounding.

Really? Why are Ryusen Blazen knives San Mai made? Why are Artisan knives San Mai made? Why do you think Ikeda knives are San Mai made? I could go on with a whole slew of knives that have a stainless core that are also stainless clad. Unless the knife is a Honyaki, it would be difficult to find any blade with a high HRC rating that the ZDP189 has that is not surrounded by a softer material for support. Look at all those knives made with tool steels (SRS-15 and the like)...they are ALL clad and they are ALL stainless. Why do you think that is? Even carbon core knives are clad in carbon so what do you think the point of that is if the carbon cladding never becomes part of the edge? It's certainly not there to make the knife look pretty. It's not there because the manufacturers are trying to be inventive. The whole purpose behind this warikomi method of construction is to give strength to a very hard and brittle metal core and this method has been around for a hundreds and hundreds and even more hundreds of years. The only differences between then and now are the materials used.

In some cases, you are right about cladding protecting brittle steels. But as you point out in your last sentence, things are a bit different now. ZDP189 is not brittle like the older carbon steels. There are plenty of non-clad ZDP189 blades on the market despite the fact that this is a relatively new material. Spyderco and Kershaw both mass produce non-clad blades. I owned one myself, which led me to my warnings on this thread.

Any dish you make will only taste as good as the ingredients you put into it. If you use poor quality meats, old herbs and tasteless winter tomatoes I don’t even want to hear that the lasagna recipe I gave you turned out poorly. You're a cook, not a magician.

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  • 3 weeks later...
Although JCK does not mention it on their website, the ZDP-189 being offered is clad in ATS-34 stainless and is supposed to be more rust resistant than the ZDP-189. Here http://www.foodieforums.com/vbulletin/showthread.php?t=1361

The working edge is not protected by cladding. Read Chad Wards tutorial. He's right that acid....Citrus..Jalapenos..onions,can rapidly degrade your very high priced ultra hard edge. Also....the POINT of ultra hard is to get a very thin,acute edge...but Hard = Brittle.

Have a tough Wusthoff or Forschner (generally QUITE stainless) for some things and have the ZDP for others. These "ultra Hard/Sharp" blades are NOT do -it -all,in fact,they are relatively specialized. Further...to get the benefits you need to LEARN sharpening skills....not gizmos and shortcuts....

Edited by Rembrant Wood (log)
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The working edge is not protected by cladding.  Read Chad Wards tutorial. He's right that acid....Citrus..Jalapenos..onions,can rapidly degrade your very high priced ultra hard edge. Also....the POINT of ultra hard is to get a very thin,acute edge...but Hard = Brittle.

Have a tough Wusthoff or Forschner (generally QUITE stainless) for some things and have the ZDP for others. These "ultra Hard/Sharp" blades are NOT do -it -all,in fact,they are relatively specialized.  Further...to get the benefits you need to LEARN sharpening skills....not gizmos and shortcuts....

I suppose this needs to be said since not everyone is a knife nut. I've experienced no degredation on my knives. I've been working with this ZDP 189 along with the Gekko, Masamoto, Hattori, Hiromoto and S1 Nenox, since receiving them before Christmas. The knives have been used to slice, paysanne, micro diced, brunoise, chiffonade, julienne and allumettes, everything from jalapenos to onions, supremes of citrus fruits and even removed parmessan rinds, there are no signs of rust or chips because they are "Hard" and "brittle". Only careless and sloppy cooks have rusty equipment. These are all based on my experience with these knives and not based on an article that someone else wrote.

Edited: to make the response more non Klingon like.

Edited by Fugu (log)
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