Weird rusting on stainless cladding

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Aug 3, 2018
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Boston, MA
Hey KKF,

For reference I'm asking about this knife: Epicurean Edge: Japanese and European professional chefs knives
Yoshikane SKD Fruit Knife - 135mm, clad in SUS-405 stainless steel

I use this knife at home for general purpose work. My question is that this particular knife is one of the quickest to rust I've ever used. I don't mean patina, I mean rust. I even tested it side by side, cutting the same ingredients, with an iron clad white 2 just to make sure I wasn't crazy. Both the core steel and the cladding started blooming orange within minutes. The iron clad white 2 didn't have a developed patina before the test and after the test only had some nice bluing. I pretty much stopped using this Yoshikane knife because I can't use it without it starting to rust. I've had and liked other Yoshikane knives that didn't have this issue. It really just seems to be this one.

Anybody have any idea why SKD clad in SUS-405 could be more reactive under similar same conditions than iron clad carbon??

Am I going crazy? I've wondered about this for a year now but just assumed I was doing something wacky...
My Yoshi SKD santoku does not have this issue.

Maybe some carbon remnants from manufacturing embedded in the stainless?
That’s really weird. Here’s my Yoshi SKD after a year with no particular care or polishing. Still a near-mirror polish on the edge and more patina on the stainless cladding than the semi-stainless core.

Assuming mislabeling is ruled out, the theory of some sort of iron dust or something is possible. People have said it can "teach" stainless to rust, maybe by disrupting the passive chromium barrier (pure speculation).
they did the hammering with carbon steel tools, thats why its rusting. and then no passivation.

you take an acid to rust away the carbon steel and then neutralize with lye.

search for:
carpentertechnology passivation stainless. will give you good results

i have tried warm 10% by weight citric acid and it seems to work.
oxalic will make everything black quite fast so you need to polish that away when done.