Morohei Hisamoto/TF mab rust help

[JJ907]

Hi all,

I have had the above knife for about 9 months but have only used it 4 times. There is (what I believe to be) rust in the low spots of the kurouchi finish all over the blade, please see photos attached.

I always immediately dry the knife (towel then paper towel) and leave out to air before putting it away. I have never had rust issues with other carbon knoves (Takamura, Misono) and don’t live in a humid climate.

Based on the photos would you be able to advise me:
1) whether this is actually rust
2) how to remove it (regarding products - I am based in the UK)

I have tried scrubbing spots with a toothbrush and baking soda. This has helped in some spots but not others. I have also tried covering the blade in a paper towel soaked in vinegar for an hour - now the “rust” seems more widespread than before. I’m anxious that I have exacerbated the issue.

Any advice on how to tackle this? The plan is to remove the rust and then force a patina … thanks all!

JJ

 

[Bico Doce]

Vinegar is only going to make it worse.

Bar keepers friend is less abrasive than flitz or metal polish so maybe start with that. That ku will take a blow but there’s not much you can do about that.

 

[M1k3]

Boil it in water. Might take several attempts. It'll turn the red rust black, and stable.

 

[Choppin]

you can try an acid phosphoric based rust remover/neutralizer. just make sure it’s not abrasive and try it on a small spot first. should turn rust black.

 

[tostadas]

Toothpaste and a brush. Mine came with surface rust all over, and this worked best for me.

 

[riba]

Toothpaste and a brush. Mine came with surface rust all over, and this worked best for me.

This 'deep clean' toothpaste sounds like it should fit the bill.

https://www.sensodyne.com/en-us/products/sensodyne-deep-clean-toothpaste/

 

[JJ907]

Thank you for all the replies! Due to easy availability at home I went with the toothpaste method and I’m definitely making progress removing the rust. Thanks so much!

Any advice on forcing a patina after? I have read to use mustard or vinegar but after my vinegar attempt above that just made the rust worse I am a bit confused/concerned.

 

[tostadas]

Thank you for all the replies! Due to easy availability at home I went with the toothpaste method and I’m definitely making progress removing the rust. Thanks so much!

Any advice on forcing a patina after? I have read to use mustard or vinegar but after my vinegar attempt above that just made the rust worse I am a bit confused/concerned.

Glad the toothpaste worked out for you!

Safe and readily available is lemon juice. Cheap instant coffee also works well. Mustard has always come out ugly for me and I do not recommend it.

 

[M1k3]

Warm cheap balsamic vinegar. A little 0000 steel wool afterwards to smooth out the surface.

 

[JJ907]

Thanks again, tostadas and M1k3!

A follow-up question because I’m eager to learn: why did the vinegar I put on the blade to remove the rust worsen the rust but vinegar/lemon juice can be used to force a patina (and the result not being rust)? Is it about rust having already been present in the first place on the blade? Or is it crucial to submerge the blade when forcing patina so oxygen doesn’t get to it?

I appreciate you sharing your knowledge!

 

[HumbleHomeCook]

Thanks again, tostadas and M1k3!

A follow-up question because I’m eager to learn: why did the vinegar I put on the blade to remove the rust worsen the rust but vinegar/lemon juice can be used to force a patina (and the result not being rust)? Is it about rust having already been present in the first place on the blade? Or is it crucial to submerge the blade when forcing patina so oxygen doesn’t get to it?

I appreciate you sharing your knowledge!

A patina, or "black rust" is just a different form of corrosion than red rust. Red rust needs oxygen whereas black rust forms in low oxygen environments. By submerging, you're greatly reducing the oxygen exposure. I don't typically force patinas so take this for what's it's worth but you might try a wash with dish soap when you're done. Whatever you choose will be an acid whereas the soap is a base and can help neutralize things.

 

[JJ907]

Thank you HumbleHomeCook, that is helpful!

(Hopefully) last question: I would like to force the patina on the tang as well because there is currently some rust on it (which I will do my best to remove) and there are sizeable gaps between the tang and the wood of the handle for water to get in. Do I submerge the entire knife including the handle? It’s pakka wood - I assume submersion might damage it?