Patina/corrosion on nakago...

[CurtisR]

Having seen some beautiful patina on nakago (nice, evenly dulled surfaces, reddish in color from age), I am wondering what would cause mine to have the "black" corrosion? The blade is by Kiyokane, and is a Showa-era nihonto. I do know to "never" clean the nakago, but do those here who've seen blades age (and who are better at metals properties than I) think this will develop to a nice patina, or does it indicate a problem?

 

I've seen rust develop on metal, of course, but haven't seen the black color before. Any thoughts are appreciated!

 

Cheers on a Friday (here in the U.S.),

 

Curtis R.

[Lindus]

On a Showa blade perhaps it would be in order to remove?,if ok try a fiber glass pen,was advised this some years ago on a Gassan tanto,worked well without being being too abrasive.

[Grey Doffin]

Do not remove the black!!! No fiberglass pen; no nothing!!! This is the beginning of what you want to develop over time. You had it right at the beginning: never clean the nakago.

Grey

[Bruno]

Maybe it is more dirty than rusty. What about cleaning it with alcohol and micro fiber?

[Stephen]

What Grey said!!!

[CurtisR]

Definitely not dirt...and I'm going to stick with Grey and Stephen on this one - I suspected it was the start of normal aging, but being Showa it was hard to be sure there wasn't a problem. Ahhhhh - relief! Thanks Gents!

 

Curtis R.

[Baka Gaijin]

Hi Curtis,

 

From the picture, you are at the beginning of the formation of a real patina, not just rust.

 

This may help explain:

 

http://en.wikipedia.org/wiki/Iron_oxide

 

Cheers

[CurtisR]

Thank you Malcom That actually explains exactly what I was worried about ; I've seen blades from the late 1500's on up, but never stopped to wonder why mine was looking as such when caring for it until now. I'm just going to leave "as is" and let future generations appreciate what comes from it :D .

 

Between tosogu and Nihonto specifics, I'm learning a wide range. Just thought.."hmmm - wonder if this is normal?". Makes me feel much better than in a century or two, it will look as it should! Metalurgy still eludes me when it comes to something older than a 1940's firearm LOL.

 

Thanks to all for relieving my worries ~~

 

Curtis R.