Rust / Chemical reactions on a kitchen knife's blade

[Giovanni_Sicily]

Hello, I first wanna say that I'm new in this forum and I don't speak perfect English since I'm Italian. I do know the basics of cutlery but I started being really interested about this world just in the past few months and I don't have any experience that's why I'm trying to take the best out from this forum and try to learn more.
So the matter is: I just bought a knife few days ago and it's the first real knife I ever owned. It's the Tojiro F-701A from Shirogami Steel, so the blade is from purified carbon steel and after few days the blade already became a bit coloured like in the pictures attached below.
Since I never owned a carbon steel knife I don't know if that can be rust or it's just chemical reaction with the acid contained in food, can you help me understanding what it is and if it can be removed somehow? Moreover can it affects the taste of the food you cut? And may you give me some tips how to avoid this? I know you can use camellia oil to avoid rust but is there any other way?
Than you for you help

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[jc57]

What you are seeing on the blade is normal formation of a patina. Patina is black iron oxide, which is a form of rust but is not the blade-damaging red rust. It is inevitable with a fully reactive carbon steel such as the white steel (shirogami) that your knife is made of.

It is harmless and expected on a carbon steel knife. You do want to try to avoid red rust, though, and remove it via polishing or sanding if it appears.

You can remove the patina from the smooth sections it by polishing using a metal polish and a cloth, if you wish. It will come back with use.

The key with using carbon steel knives is to keep them wiped clean and dry, so pretty much after every use you will want to clean and dry the blade to prevent real (red) rust.

Camellia oil or food-grade mineral oil rubbed onto the blade will help protect it between uses, if you want to do that. But the key is to completely dry it after use and before storing it.

 

[Giovanni_Sicily]

What you are seeing on the blade is normal formation of a patina. Patina is black iron oxide, which is a form of rust but is not the blade-damaging red rust. It is inevitable with a fully reactive carbon steel such as the white steel (shirogami) that your knife is made of.

It is harmless and expected on a carbon steel knife. You do want to try to avoid red rust, though, and remove it via polishing or sanding if it appears.

You can remove the patina from the smooth sections it by polishing using a metal polish and a cloth, if you wish. It will come back with use.

The key with using carbon steel knives is to keep them wiped clean and dry, so pretty much after every use you will want to clean and dry the blade to prevent real (red) rust.

Camellia oil or food-grade mineral oil rubbed onto the blade will help protect it between uses, if you want to do that. But the key is to completely dry it after use and before storing it.

Thank you very much, I guess I will not worry about this patina anymore and will just use my knife as it's supposed to be, taking care of not leaving it wet.


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