Extreme corrosion on Takeda

I am making a saya for a co-worker's Takeda SS petty and took a close look at the knife in the process and am amazed and shocked by what I saw. The core steel is darkly patina'd like most professional chefs who are not knife nerds and just own one SS-clad carbon j-knife. However, it has also been corroded to the point where it looks like a box cutter / utility knife. What I mean is the cladding doesn't even seem attached to the core. Where they meet on the bevel there are gaps between them and a big step down and the core steel looks like it has been corroded a bit back under the cladding and just all over so it is a super thin, flattish blade jutting out from a still normal shaped cladding. I'm assuming this isn't a standard Takeda thing and that it is [negligent care and] an extreme level of corrosion over time. Do you think I'm correct in this or could it be something else? Also, should I say anything?!

It's strange to me that my coworker was so concerned that I take good care of her Takeda while I have it for one day to make the saya, pointing out the hefty price tag as a sign of its preciousness, while she lets it slowly corrode away into a box cutter.

https://www.dropbox.com/s/58co4osnp21hn2u/takeda%20corrosion.jpg?dl=0
This pic doesn't do it justice but it's the best I could do :/

Yeah, I'd say that is corrosion from neglect. Given the right circumstances and enough time, i bet you would end up with an empty shell of stainless cladding. How unfortunate.

I'd expect to see something similar after an aggressive etching. But a good session of sharpening/thinning should fix that.

I would probably return the knife at once, and tell her that a saya is not for storing so she should not have one for the time being.

no_one_just_Roy said:

I would probably return the knife at once, and tell her that a saya is not for storing so she should not have one for the time being.

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I don't follow what you're trying to say. Returning the knife today with the saya, going to point out the corrosion too.

I see this every once in a while on stainless clad carbon knives that have been abused... more often than not, some thinning and refinishing takes care of it, but its a lot of work and can be a rather serious problem if unaccounted for.

Shall we call this a "sanmai peridontisis"?

wbusby1 said:

I don't follow what you're trying to say. Returning the knife today with the saya, going to point out the corrosion too.

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I think he's reminding you to inform your co-worker that storing her knife in a saya can cause the blade to corrode, especially if not oiled before putting it away for an extended time.

Matus said:

Shall we call this a "sanmai peridontisis"?

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This would never happen with a honyaki blade

Lol, not surprised.

With regards to whether or not you should say something, it's probably not a good idea. Your friend apparently thinks the knife is experiencing normal wear-and-tear. Only way you can make your point is to fix it.

i bet you that **** was left in the sink with constant water exposure countless times. probably not even aware that the core is carbon let alone the difference between stainless. petties are the most abused knives in the kitchen, myself included. my moritaka beater is both twisted and bent and scratches everywhere and a missing tip, food residue left on it, but never long exposure to water.

Update: She was actually happy to have the corrosion pointed out to her, in fact the edge had started flaking off in huge chips over the next few days of me giving it back:bigeek: (I didn't take a photo, it might give y'all a heart attack, about 3 centimeters along the edge had flaked off --all the way back to the cladding line-- and when I put it on a stone to start thinning, the rest of the edge began rapidly chipping off, truly scary)! Luckily it had chipped a couple times right before she gave it to me--I was worried she'd blame me! She took up my offer to thin it and so now it's all pretty and also I feel good about the saya I made her, because after thinning about 4mm off the edge, it still fits like a glove :biggrin: Now just please. don't. f*k. it. up. ....again. :nunchucks:

Also as to how she did it--it's her tomato knife so she cuts tomato and never wipes all service long, also lemons. Oh dear, why did I do all this for free for my new coworker!?
Also at one point she said "Now I'm going to have to buy a new knife" and I almost screamed NO!!! YOU DONT DESERVE IT! but I restrained myself, maybe I'll suggest a Kiwi for her. Sometimes I wish Kiwi's were from Japan and costed over $100 so that people who need them would buy them :biggrin:

https://www.dropbox.com/sh/wiyr6ifpd5qxxes/AABtfJBxJoKqI7c9FP-XgSm0a?dl=0


PS: what's the rec'd way to inline photos these days???

haha wow nice fix. that cook should feel lucky to have you as a friend.

This entire thread is insane! I've never seen that kind of corrosion before. I guess it makes sense though if she's cutting tomatoes and lemons with it and not wiping it off (the horror). Great job with the clean up though. Such a dramatic before and after.

Galvanic corrosion- It'll effect stainless to carbon, very much so if neglected.

Dan P. said:

Galvanic corrosion- It'll effect stainless to carbon, very much so if neglected.

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It's why stainless cladding is a great thing up until the point it becomes a curse.

malexthekid said:

It's why stainless cladding is a great thing up until the point it becomes a curse.

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Well, it's definitely a "thing".
I've also found that there will be a layer of of the carbon steel, or what used to be steel, that has lost much or all of it's carbon to the stainless, and due to being held at temperature during austenitization without carbide formation = acts basically like mild steel = enlarged grain = galvanic mayhem!

Interesting information Dan, thank you.

I bought a second-hand Carter that had been neglected in a humid climate that had this type of corrosion. It took a lot of work on the blade road with a Gesshin 400 to get it back into shape:

Yeah it is def a thing and makes sense seeing this.

In structural applications it is why you don't mix "resistant types" aka galvanised bolts witj mild steel washers. Or galvanised bolts with stainless washers... and if you go mild steel with stainless just sit back and watch it disappear. Can be a crazy quick process.

if I had to cut mass quantities of tomato and citrus, buy something from restaurant supply store that is kinda comfortable, stainless steel, less that $20, and replace every 6 or 8 weeks when it starts to get dull. was good you caught problem before knife broke.

scott.livesey said:

if I had to cut mass quantities of tomato and citrus, buy something from restaurant supply store that is kinda comfortable, stainless steel, less that $20, and replace every 6 or 8 weeks when it starts to get dull. was good you caught problem before knife broke.

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Off topic I know... or you could buy yourself one of Dave Martell's stainless petties and pay that off in a year and a bit... and it will last you forever.

malexthekid said:

Off topic I know... or you could buy yourself one of Dave Martell's stainless petties and pay that off in a year and a bit... and it will last you forever.

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Yeah, mine is my tomato and citrus knife. And it's very good in that role.

I could be wrong but I think he's all out of CPM petties at the moment though.