How serious of a problem is this?

[Autococker07]

So I went off half cocked and bought this sword last week.  It arrived to the house on the 17th.   I immediately looked it over quickly, with powdered nitrile gloves on, then oiled it liberally, and put it away.  I have had it out of its shirasaya about 3-4 times to admire quickly, each time re-oiling it (using unscented Kleenex) before putting it away in shirasaya and sword bag. Today I finally had some time to relax and take a loupe to it, under bright 5k lighting.....  and I notice this.....  (Hard to see in tiny picture, but corrosion on the Ha)

 

I am devastated, how big of a problem is this?  I have used carbon steel kitchen knives for years that have never rusted, and certainly not in a weeks time.  I feel terrible like I have failed this 340 year old blade, and would love any suggestion both on repair or general upkeep to at least contain the corrosion if repair is not possible.       

 

[waljamada]

Preface: I'm still a nihonto newbie.

 

Repair would be polishing which is expensive so upkeep is probably the path here.  Just keep the blade clean and oiled (with choji oil which does stabalize rusting) and never touch the blade with your hand/fingers.  It isn't necessary to clean and re-oil the blade everytime you take it out of shirasaya.  Truth be told, I bet that little bit of corrossion was already there.  If it just happened I assume you would have seen some active red rust (darker blackish rust is "dead" rust).

 

I actually started taking detailed pictures of my blades right when I get them so that when I later see some small flaw I never noticed I am able to check the pics to see if I did it or it was simply there the whole time.  I have yet to find a new little flaw that I actually did to a blade but without those pics I would have been convinced it was me.  It's not hard to miss a small flaw.

 

The last polisher possibly even left that there to refrain from having to remove too much metal for a non-fatal flaw.  It's a small area and the blade from that pic still seems quite nice.  

 

 

[Brian]

Think it was there before. As mentioned, left over from before the last polish. If you wipe over the blade with oil (no need for a lot of oil, just a light wiping) it's unlikely to rust. And you can't get pitting without a thick layer of rust over it.
Just preserve it as is. It won't get worse if you maintain it occasionally.

[Alex A]

Thats nothing.

 

Though i would use a gun oil like express, with a rust inhibitor.

 

Not wanting to start another what oil thread do you use thread, il leave it there.

 

Dont worry, just keep your eye on it.

[Autococker07]

Whew, thanks for the talk down yall.....    so evidence of prior corrosion may be left by a previous polisher?  

 

I was just not anticipating finding any corrosion at all, and overall the blade is much better than this one spot.    I deal with raw carbon steel a fair amount, and have never seen super aggressive rust/pitting, but have heard/read horror stories of things aggravating rust (glue on sword rack felt, etc).  As I stated above, I use carbon steel in the kitchen, but wipe down with oil each use and have never had an issue...   

 

On this sword I am using Wilson Ultima Lube II universal gun lube...... I don't know if it has rust prohibiters like the express stuff, but I use it on all my firearms, and it works great.  That said, I am not set on one particular oil. This stuff is slightly thicker than typical oil, and I like that I can put it on and see the coverage, (my eyes aren't that great anymore) so liberally just means that I can see the oil, not that it is dripping off or anything..... about 5 thousandths.     

 

I like the pictures idea.... that may be today's project!

[drbvac]

IS it actually pitting into the steel or surface rust? - could try a little ukicho powder on the area very lightly and see if it changes at all. I know some frown on it but it was a part of normal cleaning process for nihonto for a couple hundred years.  

[Ken-Hawaii]

Jim, welcome aboard. Several members have talked about rust. Black rust is good, as it's the stable, non-spreading type. Red rust is bad, & needs to be immediately addressed, as it is unstable, & will grow quickly, if you're in a humid climate.

 

Gun lube will work, but if it's low-viscosity, it might spreead easily. Choji oil is the standard. I disagree on using uchiko until you understand more about your blade's steel.