Japanese White Steel

[Acmemfg]

I own a couple Tojiro Shirogami knives in White Steel. Indeed they are ridiculously sharp and keep their edge well.
Yesterday was a huge prep day. Lots of stuff to make for a busy event filled weekend at work. After mincing a ton of shallots, kale and capers (I hate capers), the blade took on an ugly patina. Not that I much care about that, but as I wiped the knfe blade between jobs, a significant amount of "stuff" kept coming off...it was like it was kind of rusting in my hand as I was using it. The pic below is after the knife was washed, dried well, and put away; this is how it looked the following morning. The other pic is the same Santoku after scrubbing the rust off alongside a Shirogami Petty with no finish issues.

Now I know this is nothing toxic or weird but is does not look all that presentable while cooking. I have tried to force a patina on this blade using mustard, vinegar, and horseradish. All I managed to do is basically strip the kurouchi blue finish on the Santoku (which incidentally does anyone know how to restore if I were so inclined to do so?)

Point being...what exactly is going on with this blade? I'm close to retiring these blades to exclusive home use just because if I cannot remedy the issue.

Anybody?? Anyboby?? Buehller??

 

[DaveMartell]

If this blade had the black looking kurouchi finish and it's now gone then you've got problems here.

Generally speaking this type of blade construction uses either mild steel or iron as the cladding (outside) layers and is either left with scale after forging or has a faux scale look painted on the blade for protection. If either of these layers are removed, be it through use or intentionally, in almost all cases a patina will not form yet rust will. This will likely be an ongoing never ending battle for you.

 

[YetiDave]

That looks like active rust, strangely I had the same thing happen to my Japanese pocket knife (also folded steel) after I used it to cut an orange, afterwards I washed and dried it thoroughly yet it still started to corrode. I've had to sand off some of the active rust and coat it in oil until I can find a solution

 

[Acmemfg]

If this blade had the black looking kurouchi finish and it's now gone then you've got problems here.

Generally speaking this type of blade construction uses either mild steel or iron as the cladding (outside) layers and is either left with scale after forging or has a faux scale look painted on the blade for protection. If either of these layers are removed, be it through use or intentionally, in almost all cases a patina will not form yet rust will. This will likely be an ongoing never ending battle for you.

Yeah..that finish wore off very quickly with washing. Question...can a cold blue formula (like what is used to touch up/refinish gun parts) be used in an attempt to restore the kurouchi? Is it, for lack of a better word, toxic?? I really like this knife and it performs well. Is this issue (finish coming off so quickly) perhaps a warranty issue??

 

[Jim]

You can try the cold blue, it "bites" into the soft iron very well. Afterwards you would wash off the oxidizing chemicals so the finish is non toxic. Get the blade as clean and hot as you can before doing it.

Here is a cleaver I did with Brownells Phospo blue (sp?)

 

[DaveMartell]

I love the bluing Jim, if you still have this I'd love to check it out sometime.

 

[DaveMartell]

Yeah..that finish wore off very quickly with washing. Question...can a cold blue formula (like what is used to touch up/refinish gun parts) be used in an attempt to restore the kurouchi? Is it, for lack of a better word, toxic?? I really like this knife and it performs well. Is this issue (finish coming off so quickly) perhaps a warranty issue??

Well Jim showed us that it can be done so if you're feeling skippy why not give it a go. On the other hand, yes I would think that this condition is a warranty issue, or at least has the potential for replacement since I wouldn't reasonably expect a kitchen knife to become damaged in such a way from normal use.

 

[Acmemfg]

Looks like the rare beef patina method may have worked. I posted pics in a separate post today.

 

[Kazeryu]

The idea of scraping off a kurouchi finish with "normal" cleaning is a bit scary... Is it possible you were a bit over zealous?

 

[Acmemfg]

You check the above pictures of the 2 kurouchi knives I own..both used exclusively by me and both within 30 days of ownership of each other. Both were treated the same; you tell me why one finish went away and the other didn't?

No worries, both still work fine and the forced patina seems to be doing a decent job of keeping oxidation at bay.

 

[Kazeryu]

You check the above pictures of the 2 kurouchi knives I own..both used exclusively by me and both within 30 days of ownership of each other. Both were treated the same; you tell me why one finish went away and the other didn't?

No worries, both still work fine and the forced patina seems to be doing a decent job of keeping oxidation at bay.

In that case I would suspect the manufacturer.

Anyways, as long as you've fixed the problem, all is well.