View Full Version : Light Rust on KU

10-01-2011, 05:54 PM
I've been primarily using two knives for the past couple of weeks. Both knives are KU, one Yamawaku nakiri and the other a Carter IP KU gyuto. Both knives performing are beautifully, other than one major problem...they have developed a light rust throughout the entire KU portions of the blades.
I'm very familiar with carbon blades, and I'm really quite anal about how I care for them. My three other carbon blades I use (SK4, I believe, Swedish Carbon, and white 2) have zero rust, and other than a tiny spot that popped up on my Misono, I've never had an issue with it before.
My wife came up with a hypothesis that perhaps the softened water (salt pellets added into the softener, if I'm not mistaken) that I have been forced into using to wash the knives due to where I'm staying throughout the week could be to blame.
Has anyone had this happen/does anyone here use carbon blades an have a water softener? I'm wondering if my smart (and pretty) wife might just be onto something.

10-01-2011, 06:00 PM
When something changes, the first place to look is usually the last thing changed.......

10-01-2011, 06:16 PM
I can't figure out how my underwear could cause rust, but it's a start. :P

10-01-2011, 11:15 PM
Salt speeds up corrosion through the redox reaction. You might be on to something here.

And thanks for changing your underwear.

10-02-2011, 12:36 AM
I thought light rust is the normal state of affairs on KU knives...


10-02-2011, 12:44 AM
Out there ya lol. I have not had the opportunity to work in soft water areas so can't comment on how it changes things. But I would not rule it out.

10-02-2011, 02:13 AM
I thought light rust is the normal state of affairs on KU knives...

Heartily agreed with two moritakas

10-02-2011, 04:06 AM
Heartily agreed with two moritakas

Agree, if the KU isn't lacquered then it is almost inevitable.

10-02-2011, 06:05 AM
I guess I'm a bit more nuts about my knives as I don't get rust, so far. Now if I was on the line and ran off for any length of time I would see an effect, but at home I haven't and they are (almost) all KU knives. Of course they have a long natural patina growth, that may have something to do with it.

Untill that development of patina has really set in I suggest a mineral oil (or others) wipedown if not in use regularly, some KU finishes are thirsty and this help them dispace water instead of holding it.

10-02-2011, 11:21 AM
So many times I think my carbon knives are rusting but it is just patina. I think my Watanabe rusted a little and I cleaned it up but honestly I don't even know what rust looks like on carbons. Anyone care to give a few pointers?

10-03-2011, 01:08 AM
Pointers for removing rust or what rust looks like on carbon blades?

As for rust in the KU cladding, there is a real issue of removing the finish along with the rust. What I did on one of my cooks knives that he nearly destroyed was to rub the area with a coarse wash cloth dipped in mineral oil. This did remove some KU but not much (each KU finish is different yrmv{your results may vary}) and the rust seemed to come away. This was the sheet type of rust, orange and spread out on the surface. The deep pitting type of rust will not be as easy to wipe off with an oily towel. Rust forming on the non KU portion can be easily removed with a mild abrasive, you will want to resharpen if you get near the edge.

Patina is after all very similar to rust, it's oxidization, but in a good way. I'm sure the science types can correctly name the processes and all but I can never remember them. Like making beer, your encouraging a good reaction that keeps out the bad reactions. And when it comes to a patina, I'm all for the long slow natural growth as there are far fewer problems with it.

10-03-2011, 05:31 AM
Thanks for the tips guys (DC, in particular). I think I stopped the rust issue before it got bad. It was the powder type of rust, and now it seems to be gone. I have the IP safely oiled and and stored on my rack until I get back home. I've come to the realization that stainless might be a better travel knife, and as a result, I'm wielding my Misono Moly (LOVE THIS THING!)

10-03-2011, 02:01 PM
One other way to deal with rust is a product like Jasco Clean and Prime, with phosphoric acid. The acid removes the rust and leaves an iron phosphate coating behind that protects the metal like Parkerizing.