Trouble with rust on a polished blade….help

[Jon]

I’m having a major issue controlling a rust patch on a polished blade and I’m not sure what to do…I have popped a dehumidifier in the room it’s in and got the humidity below 50% ( I don’t want to drop it below 40% or it may start cracking the Shirasaya)..it’s got a good Shirasaya, I have taken to re-oiling weekly..but the rust is seriously winning and I don’t know why…it’s corroding at a speed I’ve not really seen before…I’m going to have to do something or the blade is going to suffer major pitting and likely end up destroyed and not recoverable....any thoughts.

[O koumori]

Jon,

 

I don't know the details of your situation - so this may NOT apply,

BUT if the blade was polished by an untrained person, they may have used acid during the polish, If the acid was not thoroughly neutralized, it will continue to corrode/rust.

If, and only if, you suspect that this may be the case:

 

First clean off all the oil using alcohol

Then, with a cotton ball or Q-tip, apply a saturated solution of  baking soda (Sodium Bicarbonate), soaking the affected area.

Next, rinse well with water to remove all of the solution. and dry thoroughly.

lastly, clean with alcohol again to remove any residual moisture. When you are certain that there is no water left. oil the blade.

 

Again, this should only be done if you have reason to believe that acid may have been used in the polishing operation.

 

Dan K

[Franco]

3 hours ago, Jon said:

I’m having a major issue controlling a rust patch on a polished blade

 

Old polish? New polish? Images? Oil being used? 

 

Regards,

[jeremy]

For some reason I've had this Same problem with new blades like shinsakuto.  On older blades I can leave them bone dry without oiling them during hot humid months and not a single rust mark . Types of steel as well as polish can make a difference 

[Alex A]

What oil are you using?

 

Also, need see it

[Paz]

Interesting. Where are you based if you don't mind me asking. Different climates, some places don't actually need oil. Due to low humidity. 

 

Regards 

[PNSSHOGUN]

That is not good advice, best to keep a light coat of oil even in low humidity climates.

[Alex A]

Just to mention.

 

Some modern oils use a rust inhibitor, may help

 

Such as Parker Hale express

 

plus many other modern oils

 

Plus what John said. Don't know about anyone else but in winter here i see variation in the home from 12 degrees to 22 degrees C.

[Scogg]

Being from Somerset, I imagine your climate is similar to mine (similar latitude); which also appears to be close-ish to the ocean / salt water

Over here we've got grey skies, dank earth, and frequent mold issues  - and oiling nihonto is a MUST

I use this stuff (WITHOUT THE STONE!)
https://www.amazon.c...284507_t1_B00TCZEV36

[Stephen]

27 minutes ago, GeorgeLuucas said:

WITHOUT THE STONE!)

It's a eraser...lol erase your rust away.

Actually it works on old knifes (Not Nihonto) and the microfiber is great for removing uchiko powder.

[Ooitame]

If acid sodium bicarbonate applied with a q-tip, use extremely small amount sword oil, to make it a slight paste apply to the spot. Let sit so it can neutralize any acid. The sword oil should not be an issue to the Ph. Remove the paste by using oil/alchohol(as noted below) and a spray bottle with something to catch any run or rust that gets loose. Verify it is clean, if any loose particles are on the blade it will cause scratches. Oil the blade as normal once you are sure it is clean. Avoid the spot in normal wiping. Use microfiber and very gently apply oil to that spot. Check back in week or two and see if the rust has changed color, or expanded. Please note this is not professional advise only an opionion how I would go about it... use your best judgment in what to do. May also want to check the Saya for darkspots or if you feel anything rub when re sheathing. A few pics would also help.

 

Also for cleaning %99 isopropyl alchohol, microfiber, or a lense cloth like microdear.

 

P.S. per each iteration let the rust dry, do not want a damp area that will eventually cover the spot with oil over top. Will stop oxidation but any remains residue may continue to rust. The %99 isopropyl will help greatly, but better to be safe.

 

[Ooitame]

Another idea is to talk to the original togishi if possible. If any doubts talk to any reputable togishi.

 

In any event, good luck and happy holidays!

[DoTanuki yokai]

I think it is this blade, from a similar story shared on Reddit where he said it is a reproduction sword. 
 

I would also say it’s an acid problem. 

[Xander Chia]

4 hours ago, DoTanuki yokai said:

I think it is this blade, from a similar story shared on Reddit where he said it is a reproduction sword. 
 

I would also say it’s an acid problem. 

I would assume that the acid would have been wiped away or at least neutralised by this point no?
 

“Wipe off old oil using tissues and .99 isopropyl, then use tissues and Kurobara oil to coat the blade.”, “Did not change anything to my maintenance schedule.”

[DoTanuki yokai]

The blade has openings where the acid goes in and the oil or isopropyl doesn’t  neutralized the acid.   

[Xander Chia]

13 hours ago, DoTanuki yokai said:

The blade has openings where the acid goes in and the oil or isopropyl doesn’t  neutralized the acid.   

But why would rust only start to form after 180 days?

[Jon]

On 12/19/2023 at 6:52 AM, DoTanuki yokai said:

think it is this blade, from a similar story shared on Reddit where he said it is a reproduction sword. 
 

Hi no unfortunately my blade with the intractable rust is a koto blade that was in Polish..just had it polished 8 months ago…completely at a loss to be honest as to why it’s happened….it was regularly oiled with a good quality sawing machine oil….totally gutted…it’s the first time I’ve had a blade hit with out of control rust…I did have one blade that got stuck in customs for 3 months that ended up with a small spot…but cleaning with isopropyl and regular old managed that spot easily…..I also collect old western blades and may of those are rust feasts when I get them but always managed to stabilise the rust with tried and tested isolate from moisture and oxygen….this rust on the koto…completely different.

[Franco]

Perhaps the problem is the shirasaya? 

[DoTanuki yokai]

Ok sorry then  it was just some coincidence but some pictures could help for better understanding of what goes on.